if you aren't convinced that adding the early exit generally hurts performance, well, it's not surprising; measuring performance is difficult and tricky, and you're faced here with claims you don't really have the knowledge to evaluate properly, so it's entirely proper that you are dubious about them, even if you're confused about what a proper proof would consist of

it might help your intuition to think of it this way:

1. with random input, the first ten positions of output are pretty likely (65%) to have an item that was originally in the last 10% of the input, and almost certain (97%) to have an item that was originally in the last 30% of the input. so those ten items alone account for needing 95% of the passes you'd need without an early exit, minus about five, in 65% of cases.

2. the first 20 positions are pretty likely (64%) to have an item that was originally in the last 5% of the input, and almost certain (96%) to have an item that was originally in the last 15% of the input. so those 20 items account for needing 97% of the passes you'd need without an early exit, minus about ten, in 64% of cases.

3. the first 30 positions are pretty likely (64%) to have an item that was originally in the last 3.3% of the input, and almost certain (96%) to have an item that was originally in the last 10% of the input. so those 30 items account for needing 98.5% of the passes you'd need without an early exit, minus about 15, in 64% of cases.

of course, if you're only sorting 30 items, the first ten positions of output are actually a third of all the positions, so "minus five" is pretty significant. and probably if you're sorting more than about 30 items at a time you ought to use a linearithmic sort or a linear-time radix sort instead of a quadratic sort

similarly, it's reasonable to argue that complexity (in the sense of containing many parts, not in the sense of asymptotic computational work required) is subjective, and to disagree about it

but i think these are sort of moot points

insertion sort still beats bubble sort in the situations where you have only one or two misplaced pairs of elements, and generally replaces it as soon as somebody notices

as for 'the de facto standard way of doing it today', i suggest you argue with clrs, not with me