Like many things there are benefits and disadvantages to booking on one pnr, my wife and I always book separately but we have equal status so there isn’t much to gain with one pnr, we both work so often one of us needs to make a change and in all honesty during irops it is often easier to find flights one at a time but if you want the benefits associated with being on the same pnr which are the greatest with only one passenger having status then you face the fare bucket issue, it is the same on all major US airlines,