Your explanation is all well and good, but Montgomery didn't make any attempts to partially dodge Ice Fang when he was perfectly fresh. And he had the opportunity to see the Tiger coming. I find it odd that Sedge avoided being pinned when she had to dodge rocks all around him. Thus, a bit of inconsistency.
Not sure why Sedge wasn't pinned by the rubble of the tomb. That's pretty much the norm for a collapsed rock tomb and a popular tactic. Doesn't make much sense that he sidestepped all the rubble while in a prison?
You could get a second opinion if you like but that's typically why Rock Tomb is a good move and worth using off-type Rock and Ground energy for the combo. ;o It's been a popular tactic for a while. o.o