ToME: the Tales of Maj'Eyal

So, bonuses you get from Reaping are strangely inconsistent in dependance is it sustaned or nor - sometimes bonuses are there even if talent not sustaned, sometimes bonuses aren't there.
For example I removed 1 point from Reaping, from 2points to now 1, and unsustaned talent. Bonuses are still present.
When I added 1 point - so now it's 2 point and 2.6 mastery, and still unsustained - suddenly I lost bonuses.

Hum I cant seem to reproduce that :/