I’ll chime in here, because I’ve been through this recently. The situation is the same, the company wanted the nominee to request the benefits card on my behalf, but Trading 212 are unable to do this, and I get why they can’t because it would be an admin nightmare.
That said, I approached the company anyway and explained the situation and asked if there was anything I could provide from my broker that they would accept as proof of ownership of the required number of shares. In my case they asked if trading 212 could provide an official statement of ownership with my name, address, and holding and they did accept that. Your mileage may vary.
The bottom line I think is just talk to someone, be nice, see what happens, and if they refuse then you just need to accept it and move on unfortunately. It will vary by company, and some will accept a statement from trading 212 and others won’t. They will be aware there isn’t really anything stopping you from getting a statement saying you are the beneficial owner of X shares, getting your benefits which are valid for a year, and then selling the shares. It would be completely at their discretion based on their view of the risk of someone trying to scam the system.