I think I understand what he is saying. When my middle daughter was 15, she completed her OW in a jacket BCD. Soon after that, we went by the shop where I taught, and she looked at a Zena, which she seemed to particularly like. But, shortly after that, I took her out on a coastal dive charter and put her in a SS BP / W, as that was the extra rig I had at the moment. BEFORE she dove it, on the boat ride to the site, I heard a lot of grumbling / complaining / etc. - 'It is uncomfortable.', 'I don't like this', etc. After she got out of the water after the first dive, she decided loved it, and has not dove anything but a BP since then. I do think that is a challenge at times for teenagers, and teenage females are picky enough already, they don't need added incentive by being placed in a rig that looks, well, different. (I say that as the father of three (now adult) daughters.)
There is nothing wrong with a BP / W for a teenage female, but the visual image at first can be a put-off.