I think it's pretty clear that when people say "everything is political" the "everything" is scoped specifically to scenarios where there is a decision to make and people disagree on how to make that decision.

When someone says something like "meat is political" I don't think they mean that the physical substance on the dinner plate has this property, but rather that there are decisions to make that directly involve meat which people disagree about, and that politics is the (or at least one of the) processes by which decisions get made by groups of people when individuals in the group disagree.

It's not at all clear to me. What's the point in saying "everything is X" if you implicitly mean "everything is X except all the things that obviously aren't X"?

If we all agreed on what was not political then no one would need to argue that "everything is political" in the first place, so if you want to have any interesting discussion at all then you need to actually say something about where the boundary is between political and non-political. Because it's that boundary that's contentious and might actually lead to some insight when discussed freely.

The statement "meat is political" is a different case, because it is specific. It doesn't rely on an implicit clause that hides the actual concept of interest.

It’s just how people talk. They’re not making a universal quantification in first-order logic. If you ask someone what kind of food they want for dinner and they say “I like everything” you don’t conclude that they like genocide.