"No they don't. You have a 470kg glider in UL class that has MTOM of 472,5 kg (if national regs allow). Now EASA says that you can design and build an UL aircraft that has MTOM of 600kg (if national regs allow). The 470 kg GP fits into that weight limit perfectly"

Maybe I was not clear enough and we fail to communicate.
With new EASA limit (i.e. 600kg) the national limitS are being updated.
If you check updated UL national regulations you will discover that there is more than MTOM being updated and influencing your design (Empty weight, minimum Payload, Vso, etc.).
Controlling the empty weight is certainly on the critical path to meet a lot of the requirements.