Why are digital streaming equipment manufacturers refusing to answer me?

@mihalis I called your post a "blanket statement" because you stated that nothing makes a difference when your DAC is connected thru fiberoptics etc.   There is a big difference between saying "I cannot hear the difference" and "Nobody can hear the difference".  There are many factors involved, including receiving hardware and the fact that your DAC is connected by fiberoptic is not changing anything.  I can only agree that with exactly the same data received in exactly the same format in exactly the same hardware to the same DAC - sound should be the same between providers.

Hi kijanki, thank you for the clarification which I understand. 
My statement was a straw man assumption which I put forward for us to debate. It is “absolute” on purpose, like a math equation that we are trying to prove wrong. Sorry if I wasn’t clear about that and it sounded like I was saying that I know it is correct. Which I don’t.
The revised statement which is now informed by further feedback from two designer experts is that so long as we receive bit perfect signal via fiber optic cable through a converter that is clocked to the dac we get a signal that can’t be improved with expensive streamers. One said “everything before the conversion doesn’t matter at all”.
Some other arguments against this include that one may be introducing electrical noise to the house’s electrical system before the fiber and also that one may be introducing airborne ref. I suspect these are negligible in real life conditions especially as one can move the server to another room.

I repeat this is an assumption for debate although we now have many facts in its favor. And I hope it helps people save money and focus their spending on equipment that matters. 
What I am baffled by is 3-4 responses which were not only rude but also paradoxical: bashing an effort to emulate the scientific method whilst using such science based equipment. Maybe it’s the snake oil they put on their salad. 
All the best and thanks to those who tried to explain and help. M. 

Also reading the earlier confusion about fiber optic. My bad, I didn’t want to detail the system and I should have had. I receive streaming via fiber and also play audio from local drives. All this is irrelevant to my point. My reference to fiber is only as it relates to what happens between the Roon core and the dac. My Roon core is home made and via usb it goes into something called usb pro which is basically msb’s conversion from usb to fiber optic cable. This cable then feeds the dac directly. I was only referring to this connection and not to the ISP. My understanding is that usb pro is clocked to the dac’s clock. And my search has been to figure out if I can improve on my home made nuc with expensive or well reviewed streamers. Stereophile just had such a review where the writer who seems quite honest clearly says that he can’t ascertain any audible differences. 

Hey @mihalis I had the same MSB DAC, but the lowest model, the Discrete with the same ProISL / ProUSB module combo like you. At that time, there was an audible difference to my ears when feeding that DAC via USB from a NUC, then Nucleus, vs. a top server ‘ streamer I had then, the Innuos Statement. That’s what I heard, with my ears, my equipment, my room. That’s all I needed to know, and be happy, enjoying my music. I did not have to worry why, although I intuitively can figure out the reason, based on what the Innuos Statement has / does.

All what matters is we experiment for ourselves. Sometimes new things work, sometimes they don’t. We then move one to something that works, or just stay with what we have / own. It’s pretty simple. 

@mihalis  yes, asynchronous USB receives just data and uses own independent clock for D/A conversion.  Still, any electrical connection can inject noise and alter this clock timing.  As for optical connection - it helps, but it is not a panacea.  Bits are still bits but timing of arrival can be altered.  Any system noise can make transition (including light intensity) "jagged" varying exact moment in time of level change recognition (threshold).  I don't know how to explain it better, but let's try this - Imagine in slow motion filing your tub with water.  It supposed to stop when crossing certain fill level, but water have waves (noise) and every time you repeat it - it stops a little bit sooner or later. That is time jitter.

Perhaps you know all this, but imagine that you receive 1 kHz pure sinewave.  Big electrical noise added to signal is causing different moment of level recognition and stream to "vibrate" in time.  When words fed to D/A converter vary in time then it will result in creation of additional signal - sideband frequencies.  When 1kHz stream delivery vary in time by 20 milliseconds (50Hz) the output of D/A converter will produce 1000Hz, 950Hz and 1050Hz - three frequencies instead of one (and many more at lower levels).  Amplitude of these additional signals will depend on range of time vibration, but it is very low.  It is still very audible, since not harmonically related to root frequency.  Many noise frequencies and many offended frequencies (music) results in added noise - less audible for random jitter (uncorrelated) than jitter induced by particular frequency (correlated).