Takes his diaper off at every nap. Every single nap

Started two weeks ago. I put him down, leave, come back forty minutes later to a bare toddler, a wet sheet and a very pleased face. He's nowhere near toilet training, so I don't think this is a 'readiness sign', whatever the internet says. Daycare hasn't had it once, so he's saving it for us. What stopped it for you? I'm not buying a special suit for a phase that could end next week.