They are working in a VERY inconsistent manner.
Here are the rules.
here is the column that only OWNERS should be able to change.
Except I am logged as a non owner user and I modified a formula, creating an error.
Now, the most ironic and weird thing? I can´t UNDO it, because when I try to undo, THEN it gives me the message the user can´t updated that field, according to access rules