Puppy is doing well left alone in crate, but when un-crated, immediately potties

I'm more curious than anything about this issue that's happening. I know it's more my fault than anything, but it made me curious.

I have a 9 week puppy that I'm trying to get used to me leaving sometimes. I've tried crating him, and waiting 15 min for him to settle, before leaving anywhere from 5 min to 2 hours. Usually he falls asleep and occasionally is awake and processes me leaving and settles fine.

However, I have accidentally left him out of his crate occasionally to just go to the bathroom myself for 30 seconds to do my own business, and within that 30 seconds, he will scream and immediately potty on the rug. If I am around, I know he wouldn't have pottied – it's not that he had to go – I feel like he does it out of panic or spite? It's true its my fault in that I forgot to put him in his crate before going to the bathroom or it may have been 30-60 min since I last took him out to potty, but I'm curious – is he doing this out of spite or is it just purely panic? When he's in the crate, he seems so chill. Will it improve with time as he gets used to me leaving while he's in the crate?

Thanks