Rather than tell you how I think things should work, I will give you a point blank answer (which means, I will not lie to you and will not sugar coat things for propaganda purposes).
So here it is:
It depends on the border agent and on your looks. If you look like a young Arab/Muslim man (regardless of your true identity, origin, ethnicity and etc.), and have been 1 day in breach of the RO, the border agent can report you, and if IAD shares his sentiments, you can be ordered deported, unless you have H&C grounds to overcome the removal order, or are working as an informer for intelligence agencies whose authority supersedes that of any legal authority in the most of the countries, and thus can overrule any decision by any government entity (including judicial).
Even if you are not in breach of RO, officer at POE can still send you to secondary and you will still be given a hard time, if you have wrong looks and officer at the POE is a jerk.
If you are a female, or even a man but belong to any group of visible and protected minorities, don't look like Arab/Muslim and etc., then there are very slim chances (even if POE officer is a bully and jerk by nature) that you will encounter any kind of the issue at POE for such a small (or even greater) breach of RO.
