No way to limit Brawlstars on my sons iPhone

I have tried everything and, despite limiting Brawlstars to one minute (I don't actually want him to have it at all but it seems blocking an app completely is not an option - why not?) it is just ALWAYS available 24/7. When screen time is blocked for every other app, brawl stars just pops up at any moment. Please help, this is literally ruining our family life. Please, apple, take some responsibility for this.