You don't know that. You are simply basing your statement (and saying it as if it is established fact...when it is not) on what normally occurs. I'm sure you said the very same thing about Derek Barnett. Juan James probably "wasn't ready" by most people's standards, but out of need, he was handed the starting role, and did very well.
Coleman Thomas never played OT before, and as a TF, I can see why he'd struggle. He's only played C in High School....a position I hope he returns to, this year (hope he beats out undersized Crowder).
I'm not counting on Richmond starting, but again, he has the talent and the size. Even the staff doesn't yet know if he'd be ready to start if needed. So, stop pretending to know more than our own staff does in this regard.