Are you talking about 2 Peter 3:9? If so, that passage is talking about how God is being gracious by delaying His return. God takes no delight in punishing the unbeliever, so in His great mercy, He delays His return until all that are to be save will be saved.
If God is omniscient, the He already knows who will call on Him. To deny this denies His omniscience, and thus His Deity.
It in no way is a reflection of His omniscience.
Just because He fore knows everything, doesn’t mean that he’s made it happen.
There are things my kids do and I know them well enough to know what they are going to choose. And I’m not anywhere near omniscient nor omnipotent and my knowing does not make them do it. But I’m still right cause I know them well enough.
Even so, all logic, and observable fact, indicate He leaves it to the individual to decide. I feel so strongly about that, I don't see how I would ever change my opinion - but that's just me.