Wiley
My company has recently adopted the same SOP, for the same reason.
I have seen it posted somewhere, and think it not a bad first aid measure, to depressurise the aircraft in the event of an attempted takeover (assuming above about 25000ft or so).
What next? I suppose maintain altitude until overhead, then a 2G spiral to final.... I really don't know. Any prior warning from the cabin would be useful, in any event, so a stronger door would help.