It’s slightly grey in my mind whether a 32A outside socket would attract a C2, as before 18th edition I think anything over 20A wasn’t required to have RCD protection. I’d like it to be a C2!
In this case it’s effectively an extension to the installation as the thing will never get unplugged, so the circuit supplying it should be up to current regs.
I’d insist on the RCD protection.
The risks of likelihood and consequences of pen fault versus TT and RCD failure are interesting.
With no data, if forced to place a bet, I’d go with the RCd never being tested and getting stuck one day as more likely to happen. But losing fault protection only matters in a fault, going open pen in this situation is always going to be serious. I’m not a “just TT it” person but I think it’s justified in this situation.
I’d like to see more affordable pen protection devices (as per car charger market) so the benefits of low impedence earthing can be retained in these situations.