ToME: the Tales of Maj'Eyal

How is Nature's Balance intended to work?
The language of its description says that it resets Skills of Tier X or less.
What does that mean?

At the moment, playing a Wyrmic in 1.67, I have 3 pts in it.
It says that it will reset 6 skills of Tier 4 or less.
I have 2x Breaths. One w/ 2pts. One w/ 3.
I use both of them and nothing else.
I use Nature's Balance.
It does nothing.

I put 1 more point into NB.
Now, its says skill of Tier 5 or less.
Same 2x Breaths. I use both of them and nothing else.
I use Nature's Balance. It resets them.

Is this intended behavior? If it is, the Tier X part needs to be changed a bit.
I have not checked the code, but it looks like, instead of <=4, it is doing <4 for the test.

That's a rounding issue on the tooltip. 3 points in Nature's balance with 1.3 mastery actually resets talents of tier 3.9 or less, but tooltip rounds it to 4.

Also, "tier" means the location in the category. First talent in category = tier 1, last talent in (normal) category = tier 4. Therefore the elemental breaths are all tier 4 talents and you need 4 points in Nature's balance to reset them