During 42 years I always released brakes after chock insertion, including during 7000 hours on B727. Even on A320 with brake fans, followed same procedure.
There is a story of a RAAF C130A parked on a slope at Kainantu, PNG about 45 years ago. During unloading of a vehicle, army troops borrowed 2 downhill chocks to pevent vehicle runaway. Aircraft rolled but captain was fast enough to chase aircraft, jumped aboard and applied brakes, saving a write-off.
So on a slope, depending on brake temp and company policy, belt and braces would seem appropriate.