Yes, I think you are right. However, I can't explain their intention of making it more complex to become a VIP but by the rising number of players.
I think it's normal if they make it more complex and it seems very difficult to become a VIP on their site. Maybe they need to make this change because looking back, maybe people could easily reach the VIP level so Stake had a lot of VIPs while they wanted to give something more to their VIP members.
So maybe they select their members more and only choose people who are really loyal to them to be their VIP members.