Honestly, this feels like an accounting trick to recognize taxes sooner. This helps the early year or years of the budget balance, at the determent of the later years, which usually don't count for budget scoring.

In this case, it also gives a fair number of people a bigger tax headache. In some cases, taxing earlier may mean future gains become capital gains when they may have been ordinary income; that's not good for tax revenue, even if you get some of it sooner.