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Look at where Pro road racers hands are for most of the race if you want to know how much the brake hood has become a key part of riding,

Same reason everybody who bought cross top levers for their intended purpose would - so you have access to the brakes regardless of where you're holding the bars. The suggestion is far from bizarre, your incredulity is what's bizarre here. For the sake of a couple of hundred grams and about twenty quid, why would you* not *want several additional riding positions?

You seem to be missing one important factor here...Rosie's Denti isn't a cyclocross race bike or a road race bike...it's for general riding...not off road, racing, or traffic dodging.
You yourself state that the hoods have 'become' a key position....so you must know that they weren't always, so it's no more bizarre to not use them now as it was back in the day. Gears are seen as a progression too, but it doesn't stop me favouring fixed and singlespeeds for on and off road. Same with MTB suspension...i still favour fully rigid.
Having raced cyclocross for a few years i never once used cross top levers and never once wished i had them...i rode in certain positions for certain sections of the course...i never had to panic to reach the levers.
As i've said several times before...everybody rides differently and finds certain positions comfortable. Rosie managed just fine riding 270+ miles on drops with a single top mounted lever a few weeks ago. She rides in traffic with the same setup....if she feels like changing position then she does.
Just because you feel she's missing out because you or even every other cyclist in the world thinks so it doesn't mean she is. It's her bike and she knows what works for her.