I don't know what the big deal is regarding Grant Fidelity and the Teflon caps that aren't actually Teflon caps.
Grant Fidelity doesn't manufacture the caps, they just bought them for resale, just like Parts Connection. Once it was brought to their attention that they aren't really Teflon caps, they corrected the literature on their web site.
Also, my impression was that Grant would issue refunds to anyone who wanted refunds. In the case of the linked thread, the OP bought the caps from Parts Connection.
What else is a retailer to do? Issue a refund to someone who never bought from them? Assume liability globally for someone else's product? I don't really get the extreme criticism of Grant Fidelity here.
If your local stereo shop represented ARC, and ARC manufacturers bogus preamps and amps, should your local stereo shop apologize for ARC and refund all of ARC's customers? Or just issue a correction and refund only their own customers? There's only so much a retailer / reseller is going to do here. And being overly transparent and frank just opens you up to a libel and slander lawsuit from the manufacturer.
Aside from this cap issue, I haven't heard of any other integrity problem (real, imagined or exaggerated). Haven't heard of anyone having a problem with Grant Fidelity branded tube amplifiers in this way. A KT88 amplifier seems to be a KT88 amplifier.
For the record, I do not own any Grant supplied equipment. A number of years ago I bought some tubes from them. I have never heard their amplifiers, and have no opinion regarding the quality of their amplifiers, caps, or tubes.