Perhaps Grant Fidelity adds a separate testing step but the idea that they are getting superior tubes seems ridiculous. If it helps you sleep at night and you are willing to pay more then buy from them. Or assume the risk of a more difficult return and buy from an eBay or Aliexpress seller. But the idea that tubes that are internally identical but have different lettering are functionally different seems ludicrous.
Hey @pinwa, no need to get all fired up on this. You're certainly entitled to your opinion, and thanks for sharing your thoughts!
Some people, including myself, just like to make an informed buying decision. I want to know what I am paying for, and I don't like to pay more than I have to. Since the manufacturer would not acknowledge those tubes with a different logo, hands on experiences shared by members like @danmar123 and @rocray are very valuable. Isn't that what most members are here for?
Anyway, it's all good. It's part of the fun of this hobby 😀
Cheers!