most Shanks stans think that BB will jump Shanks or "play dirty" without realizing that downplays Shanks crew. The only way that happens is if BB takes Shanks weak as fleet hostage.
In any fight with Shanks, even if BB + his whole crews tries to jump Shanks alone, the BBP will no longer be a yonko crew. They won't be able to fight Luffy ever again. Most of them will straight up be killed (like Kidd) or permanently disabled after it. The assumption here being that they play dirty with Shanks and use his allies, and Shanks mirrors Rogers personality.