True or False?

I concur with Artemis-5. I went through the same progression that he did. As my system got better and more resolving my listening skills also improved . My appreciation for music was always there but as I continually upgraded my system;I heard more details that were obscured by my earlier systems.

The better they are the less tweaks needed to make them sound good.  See how that works?

False, the more resolving and balanced the system is the more sensitive to tweaks whatever that would include, cabling, room treatment, fuses, power distributors, ac receptacles, vibration control.
As for manufacturers, they are not  denying anything for a simple reason that all use better cabling and better means of support to evaluate or demo.

We all can agree that even the best speakers respond to room placement but is it true or not true in (your experiences) that the better your audio components are, the less they respond to various tweaks?

I would hope that we all can agree that ALL speakers respond to room placement. This is after all physics. You would at this point have to find another universe for this not to be the case.

These smoking room hypothetical word games are kind of blasé so let me just say no, it is not true that the better gear does not respond as well to tweaks. Not at all. No way. Game over.