Most likely, yeah, but just on balance, if they’re already presented as travelers, then we can’t really say for sure that they were from Paldea to begin with, and didn’t just obtain that crystal while passing through Paldea from somewhere else.
(Come to think of it, Paldea’s other Legendary Pokémon are similarly unrooted — the Treasures of Ruin likely originate from China, and Koraidon and Miraidon are from other timelines. It’s interesting to me that aside from Terapagos, none of Gen 9’s Legendary Pokémon are originally from the place they first appear in.)
Indeed, and there’s even other minor cases like Corphish and Yungoos, which from the beginning were characterized as being invasive species in their Pokédex entries. I just think it’s funny that even if they were to specify that the Kitakami legends are from Kitakami and not Paldea, it still wouldn’t actually be correct — it’d just be slightly more accurate to the context in which they were introduced.
Really though, this all just stems from TPC preferring the more immersive framing of “this Pokémon was first discovered in the Hoenn region” over “this Pokémon is from Gen 3.” And from that perspective, I guess it’s like, if they’re already using “Paldea” as an obfuscation for saying “Gen 9,” then there’s not much point in distinguishing further between Paldea, Kitakami, and Blueberry.