It’s a hundred or so grams of difference, which isn’t too far removed from changing a steel post to titanium. Won’t change the handling much given its location on the bike, but if you’re dropping weight on a fancy expensive build, it’s an easy place to do it.
When I switched my Brompton to Hollowtech (105 5800) and was surprised to find the weight of the components was pretty much identical.
Square taper BBs are still shit but weight isn't the reason why.