Schiit Saga+...What’s the point of the tube?

I’d say that discerning the differences between tubes of the same design is an advanced listening skill.  Don’t draw conclusions like that as a newbie.

I have had similar experiences with tube buffers. I could not hear a difference.
I have found the quality of the volume control to trump everything else in the preamp regardless of the rest of the design. 

For that tube glow. No matter the topology any amp can be made to not impart a sonic signature in other words the distortion is low enough not to color the sound.  I would guess that's the case here. 

Lots of folks here blovulating with zero understanding, kinda scary.

 I have the original Saga, the Schiit literature clearly discusses that it is a tube buffer on top of a no gain device. 
The tube thus has a variable impact, depending upon the input impedance of your amp as well as the usual other variables in any system. Used in my case with three different amps, two SS and one tube, in all cases to me it sounded fuller with better 3 dimensional shaping of instruments and the soundstage when using the tube buffer.

It is a very clean sounding device with more resolving power than my Audio Research SP6B preamp. It does not have the natural 3-D soundstage nor sound as natural and effortless as the SP6B, but I wonder whether it was fully burned in when I was comparing it. I think it has hugely improved the sound of my bedroom system (Adcom GFA535II and ATC SCM7’s). Tremendous product!