Wow, three pull-ups is nothing! My daughter could easily do that.
My son is a Marine, and before he even considered applying to the USMC he could do 20.
That they have not achieved this already points out how very, very little physical training is in their regimen.
They do not belong in a combat MOS.
On the other hand, if they have already put them in a combat MOS then it is less damaging to go ahead and put them in combat than it is to have them filling up all the destress billets and deny combat troops a place to wind down between combat deployments.