One has to take Marco's quoting the 6moons.com interview of Professor Kron as the true. And, as Marco states, this was a different tube than the JJ (Telas/Teslovak).
I have no experience with the KR KT88, apart from seeing a pair of amps with them. They are far larger physically than a JJ KT88, with supposedly more power and extension. As far as the "tone" of the tube goes, or the claims of superior power/extension, obviously, I cannot make any comment regarding that. There is so little opinion avaible about them sonically that they remain more or less an unknown. I REALLY lament the missed opportunity of not giving them a listen.
One would surmise that if JJ felt the KR KT88 superior, they would have either continued on with the design. Or, if doing so violated any agreements, patents, trademarks, etc., they would have still incorporated elements of the overall design in their own tubes. Perhaps this has not yet happened, but will in the future?
Marco is also correct about rebranding tubes. This was de rigeur during the halcyon days of tubes. There are hundreds, if not thousands of examples of this, such as the treasured Amperex/Bugle Boy tubes which were made by third parties (normally by Mullard, Philips, etc.).
Aside from all of this, one has to label the second hand nature of the statements regarding the KR KT88 being compared sonically to the British Gold Lion tubes as such. While, it may or may not be true, until and unless someone who has actually tried both steps up and says this here, or we have a tube shootout, it comes across as not having much behind it.
The KT88 in current production that I like best is the JJ. For my money, they are head and shoulders better than the Sovtek and EH variants.
Finally, I hear a lot of good things by people I respect regarding the Shuguang/Penta tubes, but have not personally heard them. I will say that I wouldn't discount the Chinese tubes offhand. As utterly shocking as this assertion will sound, in my own experience, the current Shuguang 12AX7 bests a lot of the NOS sacred cow 12AX7 tubes. Now, if they'd only redo their EL34...