I don't think this is the case, or at least, I'd expect it to be a bug. Protocol Buffers should generally be non-destructive of the underlying data. That means

I don't think this is the case, or at least, I'd expect it to be a bug. Protocol Buffers should generally be non-destructive of the underlying data. That means even if it encounters the wrong wire type for a field, it should simply retain that value in the unknown field set rather than discard it.