Waiting for naptime to poop

Why does my toddler keep waiting until his nap to poop?!

He usually wakes up for the day around 7/7:30am. Breakfast 8:30/9am and then down for a nap around 11am.

For this past week, he's been refusing to nap until I found out that it's because he pooped!

He'll happily sit in his crib rolling around and talking to himself for an hour, but it's obviously better for him to get a little rest.

These past 4 days, my husband and I decided to wait 15-20 minutes after putting him in his crib, then we go in, change his diaper, and put him back down and he'll usually fall asleep.

It's just so weird!

Anyone else?