I have Nauticam housings for the 502 HD monitor and Canon R6 that I bought recently. The thick HDMI cable passes through the monitor housing without interruption. However on the camera housing there are two connections required at the bulkhead, both micro HDMI
Inside the camera housing is a much smaller wire with male micro HDMI plugs at each end, one going into the camera and the other to the bulkhead. I think it's this wire that has the bad reputation.
With my setup, Nauticam didn't take advantage of the larger M24 opening on the camera housing since a M24-M16 step down adapter is required to mount the double female micro HDMI adapter.
The problem is you have to back out the camera each time you change the battery, which requires slack and flexibility. The HDMI 2.0 cable is way too thick for that and needs to be reduced to a thinner cable. In the monitor housing, which uses a full size HDMI plug, you can connect it and not have to touch it for the entire trip, or forever as long as the cable stays good.
I have been very gentle with these wires and have not had a problem after close to a 100 dives. I do travel with spare cables and would factor in that cost when buying these monitors.