I can see why Sammy wanted SEGA: They had IPs that would work with their machines, they own amusement centers and obviously operate the same way (arcade games/Pachinko slots are popular in Japan due to foot traffic).
But yeah, their separate companies. When SEGA released all those games that failed (but we liked around her) it was Sammy's money that kept them going. I don't think pachinko slots are bad, in the end its just a machine. You don't get mad at weapon manufactures for making guns, but the people that use them irresponsibly. I don't know exactly how Sammy runs its business, but like stated before its up to the operator to set the number of wins.
Honestly if Sammy didn't allow this, someone else would and Sammy wouldn't be #1 in the pachinko slots market. Its a shady business and can become illegal at any time, I'm not shocked that Sammy has been spreading their roots just in-case one market dies out. (They own anime studios, Atlus, Index, Toho Animation, Marza, Sega Toys etc etc)