ABS fragility comes from doubleshotting, the spacebars are single shot as they're one colour. I wouldnt worry about it.
FWIW, I've mounted an unmounted yuri several times without damaging a keycap, i think this fragility is overblown if you're using them with SKCM switches, I believe matias stems are much tighter so I could well believe they'll break when pulling from matias.