Suppose a character has perception B1 (maybe they are a young troll or something). If they open their observation skill, either in character burning or through play (testing, practice, instruction). Are all of the following consequences true, or have I misunderstood something? The points are in no way specific to perception and observation; those are just examples.
The new skill opens at B0.
The new skill can not be rolled, even with artha. That is, it is no longer possible for the character to even try rolls they could try before opening the skill, even under neutral or favourable conditions.
The only way to reacquire the ability to make observation tests is to get practice or instruction to increase the skill to B1. (In character burning, one might have extra skill points to increase the skill beyond just opening, but let us ignore this for now).
The consequence number two seems quite unintuitive, which is why I am asking.