Pressing the button interrupts the charging, the ring will turn blue for a moment while the charging is reset, then, only if charging restarts, it will begin flashing green again.
Here's the problem with this, however:
1. You are messing with someone else's vehicle before you even know the status of their vehicle.
2. This could unnecessarily concern someone to return to the station when not required to.
3. If you do this at anything other than a Tesla Supercharger, or Tesla HPWC, you run a high risk of the charging not resuming.
4. I really don't think anyone can determine the exact SOC based off of the flash rate. It is just not that finite of a difference.
5. Even if you could determine their exact SOC based on the flash rate, who are we to decide that they have received their fair rations and should move? Again, we don't know their specific situation.
Trust me, I do see both sides of this. And if I were in very bad situation, and I had already checked PlugShare, and there were no other charging options, and I couldn't locate the owners, then maybe I would resort to this, but only in an emergency.