What we can say for sure that this discussion will lead into nothing but wasted time. One says we tag A, the other one says we tag B and nobody will agree with other persons point of view.
The access situation is so unique that the the momentarily situation can't be tagged entirely correct in OSM.
The lift gate and street beind it follow the same access rules. If you can access the lift gate (or bypass it on the road) you are more than likely are allowed to drive on said road.
However, the road doesn't even have an access key in it. So if somebody thinks that the lift gate is not the place for the access key, said user should tag the road. Instead said user did remove the access key about 6 years ago.
@ fkv: Mind your language! Just because somebody is focused around fixing mapping issues does not mean he has no "personal interest in improving the map". We also don't claim you have no personal interest in improving the map as you only accept your ideas and treat the map rather like your personal property than a community project.