If you're running a sportsbook there are two paths you can go down:
Offer lines that aren't competitive with other books, and only on main stream sports/leagues, but never worry protecting your edge against sharps/insiders. That means you take any bet from anyone and everyone has more or less the same limits.
or
Compete to offer the best lines, either ban or limit those who you suspect might have an edge, and increase limits for players you're confident are recreational players.
If you offer competitive lines and don't limit sharp bettors, you're going to go bankrupt. In the end, for a bet to be valid, both sides have to agree on the terms. When a player is limited, and then bets more than that limit using another account, that's a bet that the book did not agree to, and the player knows that when they try to make it. It's as simple as that.
I read they have quietly cut off half of their rakeback while saying they have increased the bonuses given to their customers, is it true?
Yeah. And it was really messed up. They can make it whatever they want, but doing it without any sort of warning or even notification when it happens was really disappointing to see. I immediately complained about it when it happened.
AFAIK the sportsbooks with the highest RTP, Pinnacle for example, don't treat their customers like that, by selectively discriminate them, and always stay professional. I don't know how their business work but it's not by doing shady things like that.
Stake takes advantage from being a crypto offshore casino, and not being as famous as largest sportsbooks but if it makes bad things with their customers I don't think australian authorities will appreciate that, neither american, canadian and english ones since it is doing business with sport organizations and personalities from those countries for advertising.