This is exactly correct. Resistance focal point is the condition type, not the "effects". The condition type is the determining criteria. The effects are what the condition does, not the condition in itself. That is why resistance doesn't work on it, and logically that is a sound decision.
Also, the negated healing is technically net damage. While it is not delivered in damage packets, it is subtracted from health packets. A net loss, and by some, including myself, is still considered a source of damage. This is why the sigil of doom is so popular as a pick, regardless of build type.
Now, they could re-categorize the poison as a non-damaging condition that reduces healing by 33% and also causes damage if not under the effects of resistance. Effectively working the same, but appeasing the opponents of its current form.
Could be a difficult change though, surely there are more prevalent issues to focus on as a dying community.