Creepers spawn during in high light levels

I was just playing survival and I exited my house when suddenly, there was a creeper. It was daytime so it shouldn’t of even spawned in the first place.

What I expected to happen was...:
When I exited my house, there shouldn’t of been a creeper because it’s daytime.

What actually happened was...:
Instead, a creeper spawned

Steps to Reproduce:

1. make a huge box

2. light it up with torches

3. wait