On the other side of that argument, I have dedicated arrow keys on my 60%, in addition to the layered ones.
That setup allows me to use whichever set makes the most sense, at any given moment.

If my right hand is on the mouse, and going back to it, I will either use the dedicated arrow keys, or use WASD with my left hand, surrounded by Backspace, Delete, Pg Up, Pg Dn, etc...
If my right hand is on the mouse, and needs to go to typing position next, I will move it straight to the home position, then use the layered arrows on IJKL, also with the nav cluster keys around them.
If my right hand is already in typing position, I will swap to IJKL, on the fly, then resume typing, without ever moving my right hand from home position.

Moving my hand off the home position, to go use the dedicated arrow keys, then moving it to hit a follow-up key, like Backspace or Delete, then moving it back to home position, is completely inefficient.