What is his objection to using the RSTVs? :scratcheshead:
You can't use the vests or boosters on the plane, and bringing the boosters would be a much bigger hassle IMO. You can't check them (checked = crashed, including gate checking), unless they're well padded and packed in a sturdy box. So that leaves trying to carry them on, which again is likely to be a huge hassle. It is frequently recommended that if you must travel with a booster, to pack the back in a suitcase, padded on all sides by clothes, and then carry on the bottom part. But I'm not familiar with the Jane boosters, and don't know how easy they are to take apart and put back together.
In any case, there's a reason the vest is called a travel vest. They're so small and lightweight, it makes them ideal for traveling. I can't imagine choosing to bring a high back booster instead. :shrug-shoulders: