I am surprised as a pilot you don't understand the reason for that rule and the differences between the aircraft generally used.
The same size hole in a typical 135 aircraft will depressurize the aircraft much faster. Many 135 aircraft to not have the warnings and back up systems for pressurization a 121 aircraft will have. All 121 aircraft have to be certified to descend to 10,000 feet in a minimum amount of time. That is why max cruising altitude is often well below what the aircraft can actually do. 135 aircraft can fly higher.