Why need XLogReadBuffer have the paramter "init"?

Cann't we remove this param?
We can rewrite like this:
1.XLogReadBuffer:
* remove init;
* everytime we cann't read a block, just "log_invalid_page" it, and return
InvalidBuffer;
2.Also rewrite all functions calling XLogReadBuffer with "init=true": skip
current block if XLogReadBuffer return InvalidBuffer. e.g. replace
Assert(BufferIsValid(buffer)) with:
* if (!BufferIsValid(buffer))
return;

Is there any harm?

Another question: if oid counter wraparound occured, and one relfilenode was
reused, e.g. see the following sequece:
1. Once there was a rel with oid XXXX;
2. Then it's dropped;
3. Then OIDs counter wraparound occured;
4. Another rel was created, and reused oid XXXX;

If there's no checkpoint since the first step, and system crashes after step
4, is it possible that the new rel's data be destroyed?