Had my 2016 Sierra in for service at gm dealership, they were doing a transmission flush ( I do all my maintenance at the dealership), when I dropped it off there was no check engine light on. When I picked it up there was. Checked the codes and it was showing p2736, the service person and the tech said it will be fine, just drive it for a bit and the code should go away. I took it hooked up my reader, cleared the code and it came right back.

is this normal for the service dept to release a vehicle with a check engine light on the part of the vehicle they worked on and say it’* fine?

No.

P2736 indicates the pressure control solenoid in your transmission is not performing as it should.

This would appear to be a direct result of their activities. I wouldn't drive it with improper transmission pressure. You could have slipping, hard shifts, or other problems that will cause permanent damage. Have them tow it back for repair.