Big mom being in WCI makes no sense and is probably non canon
if big mom just went back to her island, with her same old crew and territory, then why would she have lost her seat as yonko?
Luffy literally replaced Kaido as yonko. Not only did he defeat the beast pirates, he’s claimed wano as his territory.
Therefore it only makes sense if cross guild replaced big mom, conquering most of totland(I believe the cover story isn’t up to date on current events). If big mom hasn’t been replaced, then how could she have lost her yonko seat?
imo, the movie just didn’t want to reveal the new yonko or anything that would happen to linlin or her crew post wano.