Cannot fathom the USN choice either as the LOX system had many dangers (not all cited in this forum). When new a few pilots from the prop era lit up ciggies in the cockpit only to be burnt to a crisp. My A4G instructor demonstrated the 'flame' effect by hoping out after flight to go off a safe distance to then light up a cigarette and blow through it producing a prodigious flame - this same demo cited in a classroom lecture in USofA.
The first A4G lost from a cold catapult shot had the pilot go in (with canopy jettisoned) underwater breathing that emergency oxy whilst MELBOURNE passed overhead as he scraped down the side still sinking. Once he heard the screws go by he left the cockpit and the emergency oxy behind, inflating mae west to 'pop up' behind the carrier only a little worse for wear.
Attached is a 3 page PDF about potential 'air-mix' system for A4Gs after a fatal TA4G crash at sea with particular pilot LEUT Ralph McMillan suffering badly from 'the cough' which had been investigated earlier by our resident 'A4G flying doctor' LEUT Michael Flynn.