The fact is that your adding or removing an extra lens.
Someone who normally wears glasses will set their scope up to give them the best optical performance with a set PA (exactly like everyone else). If you then remove your glasses you will get a different optical performance with your set PA. Usually with a short sighted person you will get a clearer view of the closer targets. A none wearer of glasses would not have this advantage.
Is it cheating. Yes, if it gives you an unfair advantage over other shooters.