Air Canada tested beards on their aircrew in 2018 the report is online I believe, it showed no adverse O2 issue with either on demand or pressure systems. This is simply those at the top disagreeing with a policy and using Kneejerk reaction to block the issue.
Basically those at the top of 1Gp/2Gp are so out of touch with reality, they need to adapt and move on from the bloody 1980’s . Here is an idea pay for a study and stop being finger in the air wind blowing response artists !