But no one is looking at the register, you are supposed to remind everyone what you put in there every time it's relevant. This is a very unusual way to use a register...
Land is also registered, and if someone starts building on yours you tell them "Hey stop, that's my ground you're building on!". What's the difference here? The registry is there as backup proof you can point to when reminding people; isn't that how they work in all these situations? Seems the perfectly normal default way to me.
The law says they can't build there. If they do it, they are already breaking the law, because they were supposed to know. If the rightful owner doesn't react in time to stop it, they can still order the building to be teared down at the infringer's cost.
This is exactly my point, it is completely different from how the trademark registry works, were people are not expected to know. They can make their claim, and if no challenge happens, they will make it to the registry. They can do this without prejudice and rectifying the situation falls on the previous owner who has to spend significant money to make a case (one they can lose).