It was interesting for me to see on Monday morning that Alaska Airlines sometimes uses the aircraft’s rear door for boarding the back rows of the airplane. It’s not something that is done often !
I think there are studies out there that show that boarding all window seats first, then all middle seats, then all aisle seats is the quickest – but to do that in practice is a major challenge. The airline will likely upset the super platinum elite frequent fliers that like to all board first – to go sit in the front of the airplane, or to go sit in their chosen seat further back.