Upon landing, the criterium for stabilisation is aircraft speed under control and generally ECAM procedures -if red- shouldn't be undertaken unless pbrake is on, airplane on the runway.
I agree, except that in this particular case unless you move the T/L to Idle you will never slow down enough to set the parking brake. This warning can only occur under certain conditions at one specific point in a flight, unlike most ECAM warnings which can occur at any time and therefore need general rules/SOPs. For any warning the priority is a/c flight path - e.g on an EFTO it is not a case of doing absolutely nothing until 400' agl... you raise the gear, trim, engage AP etc. I don't see moving a T/L to Idle as any different in this situation - PF should have done it anyway. As the warning exists I shall have to train pilots to respond correctly.
Whether the crew have the capacity to understand the significance of the ECAM warning under extreme pressure is another question altogether. For a crew to work out that lack of Ground Spoilers and Autobrake means "T/L not at Idle" is very unlikely IMHO, so this new warning has to be an improvement. It will need suitable training to highlight the fact that it exists - IMHO by instructor demonstration as you should not ask a trainee to make such a mistake on landing.
Cheers, Tyro