If it works for you, who am I to rain on your parade?

But it wouldn’t be my choice.
1) I really try to avoid riding with so much gear in a backpack that an external frame backpack would be needed. Added pressure on butt, hands and arms.
2) where EF packs have their strong side is to be able to carry the load high. I much prefer keeping the weight low on the back for riding.
3) I find that the frame interferes with how I like my back to curve, and occasionally twist during riding.
4) even at 6000+ miles/year, backpack wear is quite far down on the list of commuting costs.
5) by now, I’ve gotten panniers that do the job with greater comfort and sense of control than big packs.