3/4" adapters not safe?

[WSSix]

So I am about to pull the trigger on adapters for my TA. I'm putting BMW M-parallels on the car. I can run a 3/4" spacer on all four corners. I have gotten quotes from a couple companies for 3/4" adapters. However, I have had one company tell me 3/4" isn't enough meat around the studs. That's the studs that are in the adapter. My question is how is 3/4" not enough? Yeah, it's billet aluminum instead of steel but the axle flange on the rear of my car is no where near 3/4". I believe the thickness of the front Kore3 hubs is right around 1inch at the studs. With what I know and understand 3/4" is plenty. However, I'm not arrogant enough to believe I know everything. So can someone explain to me how 3/4" could not be enough? All companies use the same grade aluminum.

Thanks