Last week I had boarded a flight at LHR and the crew were just starting their safety briefing when everyone's phones went off with that wildfires 'emergency' alert message.
I was unimpressed with the message, along with the (non-UK) crew.
My completely unsubstantiated impression is that it was the govt putting out a feeler on whether it should use the alert system more frequently (and afaik it was relatively unpopular)
I'm puzzled why your entirely factual and relevant statement documenting your experience has been downvoted.
Would a downvoter care to explain themselves?