I do agree with this point.
Okay I'm gonna be blunt, IMO steels like The Thing JP, Terminator 4 Virgin, Hugo Korea, Avatar JP, Ted Korea and all the other limited Asian releases with a silly slip (no offence to anyone who has these) that have sold for silly prices I do not class as a grail...you can argue I am being biased if you like, I'll take it like a man
The reason I do not class these as grails, even if they were sold for a high price which I know they have, is because of the lack of general interest and appeal to a majority of collectors.
Steels like Gladiator TW, T2 2.0, Thor JP, Terminator 4 TW, CA TW, TDK FNAC, IM 2 JP - these are an example of steels with a silly sticker and slip that will fetch silly prices have a large appeal to collectors.
Steels like The Thing JP, T4 Virgin etc will appeal to a minority of collectors that will pay silly money.
The definition of a grail can be a subjective definition to everyone.
To me it has to be highly sought, popular, expensive, and rare (but not always, IM FS is an example).