They did that last tier because at the beginning you only had 3 pieces that gave you the bonus, then they added the other 2 to make it easier to get the effect.
They dont need to do that when we already have 5 pieces that give the tier set bonuses and we are getting this new system to make whatever piece we are missing.
There is 0 reason to make crafted bracer/boots count as part of the bonuses, if they were going to do that then the ones we get as raid drops would do the same.
It also doesnt make any sense that when they have this line in the same post
They go out of their way to make sure people understand that bracers/boots DO NOT count as part of the tier set bonus. There is 0 room for interpretation.