Puppy has learned not to pee in pen but pees elsewhere in the house

We have two new mini goldendoodle puppies around 3,5lbs. Brought them home at 8 weeks. They are now 9.5 weeks.

They are getting good at going outside as long as we take them every couple hours, pushing it to 3.5 in the night.

They have crates and a play pen that’s 4×8” or so. Initially they had some accidents in the pen, but they seem to have figured that out and when we open the gate they will head for the back door.

But if we take them to play in another room while we are doing stuff, they’ll pee on the floor. This happens even if we’ve just taken them out.

I’m wondering if this is just because they know their pen is their space and they treat other rooms in the house like they are outdoors.

What’s the best way to get them to understand the rest of the house is not the yard and to always go outside?

At first they were having accidents in their