Why not set builder->next_phase_at=InvalidTransactionId in SnapBuildRestore function?

Last email has some problem, I resend one.

In PG14 or higher version, I notice that SnapBuildRestore function don't set builder->next_phase_at=InvalidTransactionId .

But in SnapBuildSerialize function, the assert check this condition.

Assert(builder->next_phase_at == InvalidTransactionId);

I'd like to know is this right?

Thanks.