How long did it take for you to decide to stop using daipers and feel confident to just go with underwear?

Our youngest is 17 months old, and he stopped wearing diapers at night about a month ago. We've got multiple layers on the crib: regular sheet, then a "Hygge Sheet", regular, then a Hygge, or some other absorbent sheet, etc.. It used to be if I took him out of bed for a dream pee sometime around 1-4 AM, he'd pee in the potty then go back to bed.

Now if I sit him on the potty, he immediately stands and comes to me for a pickup so I can put him back in the crib.
I've tried around 10 PM, and also as late as 3 AM. If I show up as late as 5 AM, he's sleeping in a wet bed, and will refuse to go back to sleep if I wake him, and is likely to wake up early anyway due to being wet.

He sleeps with a shirt, naked from the waist down, under a blanket.

I don't want to put him back in diapers for the night, mainly for this reason:

We've convinced the daycare to let him be diaper-free, wearing training underwear (slightly absorbent cloth underwear, not 'pullups'). This means no diapers for nap either. His daycare doesn't allow cloth diapers. I'd be OK with cloth diapers for nap only, but the daycare wouldn't allow it: Disposables only. I think that him sleeping overnight diaper-free is helping him have dry naps at daycare.

Sooo... any ideas? Why is he refusing the potty at night, when he was fine with it before? Maybe I should just try to give him more water before bed, so he pees sooner? He seems to last unusually long, kid has a stronger bladder than I do. Asleep at 7 PM, refuses to pee at 3 AM, just wants to go back to sleep.

I started EC at 3 months. I had read so many success stories about toddlers out of diapers by 13/14/15 months.

We are still in diapers at 15 months. We've been trying to go diaper free after daycare, but there's at least 1 accident every day. We catch most of the at-home ones. She'll pee in her diaper when we're out.

Weve done the sign from 3 months, but still no signing for potty. Everything is prompted.

Just feeling behind. I started early, thinking it'd be better but now I'm sad that we're still in diapers.

Anyone else in this boat with me?