Such fragments don’t need to be particularly human-readable, only machine-readable. Given that, greater flexibility is generally a virtue: different matching strategies will work better in different contexts, and different tools can benefit from it. Consider the increased scope of the annotations feature—it’s designed for things like more robust referencing, bookmarking with annotations and other things like that.

There then remains the question of cross-compatibility: do all relevant tools implement the same techniques? That is a legitimate concern, but it’s well-enough specced that it shouldn’t be a problem.

Also as noted, various tools out there already use this format. The Chrome team ignoring that and using their own, functionally inferior format is hostile.