Not really unfair, since all international standard cards are by definition legal in Japanese standard. If you're playing at a high enough level to get into worlds, the differences between our formats aren't that hard to adapt to. Some international players make it to worlds based on performance in expanded events, and expanded is functionally almost identical to JP standard with the addition of a few key cards like lasers, PLF eggs and colress.
I actually hope they take this year's rotation as an opportunity to synchronize our formats, since we will both likely be moving to SM-on and could be painlessly adjusted to a simultaneous rotation schedule, though it would be hard to do this on a set by set basis because Japan's releases are structured differently, around more frequent releases of smaller sets. The Japanese approach, taking whole blocks as meant to be played together, makes more sense to me than rotating on a set by set basis which kind of arbitrarily cuts us off from important cards, like when we lost tool removal for a few months early last season before Guardians was printed.