You sure about that? I lived in both states and don't remember it being that way.
According to Kaiser, pre-ACA only 5 states had guaranteed issue, and PA and TX weren't included.
That's not GI. You don't want that. However, carriers generally honor each other's pre-x's.
I remember my husband quitting work in Texas to become self employed. I was pregnant at the time and bought Blue Cross and was told that I would be covered at the ‘group rate’ and I was. I had a high risk pregnancy and birth with a child in NICU and 60K in bills and it was all paid for. I remember something similar in PA, but that was a long time ago.