What exactly happens if fetch size is smaller than the next batch (0.72 and high-level consumer)

Hello -- I'll try to look at the code, but I'm seeing something here
and I want to be *sure* I'm correct.

Say a batch sitting in a 0.72 partition is, say, 5MB in size. An
instance of a high-level consumer has a configured fetch size of
300KB. This actually becomes the "maxSize" value, right, in
FetchRequest? So in this example does the high-level consumer stall?

Thanks,

Philip