Just looking at that one picture, he looks pretty lacking in mobility. He isnt overweight, so that will be in his favor.
My prediction is 11 minute pace, which may be too generous. That makes for a 4:48 finish time.
Also, it looks like he is going to be doing his gym's WOD, not necessarily the national xfit WOD. The national xfit WOD has very little running. It is a bit disingenuous that he is doing "only" xfit WODs as his marathon training since it is his gym and he is writing the WOD. Maybe his gym "just happens" to incorporate lots of running. Even 15 to 20 mpw snuck into xfit training would make a massive difference in marathon prep compared to no or almost no running.
If he did the national Xfit WOD, I would give a 50% chance of not even finishing, due to blisters.
This is the national website's WOD, for reference:
https://www.crossfit.com/workout/