The key terms here are "slots in as starting center" and "compete." He does have a genuine chance to win the job. But he is not entrenched. You just don't know how the draft will fall and whether it's Bradbury, McCoy, Lindstrom, etc. there are quite a few interior OL that the Rams could draft.
I like Allen's intangibles a lot and his intelligence, work ethic, wrestling background, all that will help him. He does also simply have to get stronger and add a few pounds and I'm sure that's happening now.