If an instructor is carrying out dual instruction (and is therefore PIC) with a PPL or with a student - providing there is no one else on board - he is not flying with passengers.
In theory, that instructor could be way past 90 days and still be legal. Doesn't make it right of course.
Dead easy, at the end of a training session, to say; "Let me show you a slightly different landing technique." Or; "Do you mind if I do this landing?"
I've never been refused.........yet.