They explained it quite well, I got this message from them

Hey Homo sapien,
Just saw your thread on the delay with processing your welcome offer,
Our apologies you had to wait, but happy to see it went through for you!
As you can imagine with a good risk-free welcome offer we get many people trying to take advantage and trying to ruin things for everyone,
so if we have a few flags go up we will request some ID docs. Nothing more than trying to make sure fair people get a fair offer!
What is your account username at Sportsbet.io?
I'll drop some mbtc in there for you for a free bet for your troubles Wink
Cheers,
Justin

And spammers please stay away, as I have every proof my deposit, first bet and everything. I also have screenshots of chat and mail that they send me regarding document verification.