Harbin Osteen wrote:

Is it not correct to have the EPIRB already on deck in a
self releasing holder? That is if it is not a personal EPIRB.


Not necessarily for a catamaran - The presumption is that if the boat
flips, and anyone is left on board, they would be able to take it out
of the locker and activate it. Having it on deck increases the chance
it would be damaged, lost, or inaccessible when needed.

The fact that it was found in a locker implies that the entire crew
was on deck when it flipped. Certainly (we can hope, at least) anyone
down below would have activated it even if they were trying to escape
or rescue the others. Since this was a professional delivery team we
have to assumed they all knew where the gear was, and had discussed
various emergency scenarios.