Sim free or pre activated?

I cant complete the ordering process for the 10 Pro when I choose SIM free.
Is there a diference between these versions?
My carrier is T-mobile.

What @Wolfie said.

The furthest you can get in the process right now is pre-approval for the iPhone Upgrade program, and picking out which phone you want to order on pre-orders open on Friday.

I’m on AT&T and the iPhone Upgrade Program. I was able to complete the pre-approval process. The phone will come with an AT&T SIM but will be unlocked.

I’m not sure about this year, but I seem to recall that in past years the SIM-free option was delayed for a short time.