I was 6'3" and weighed in around 150 pounds. So I was very scrawny and had not enough upper body strength to do the pull-ups.
The PCP platoon was mostly for fat-bodies, who could not do the required 3-mile run within 28 minutes so I was unique in that running was my specialty. I was doing sub-20 minute three mile runs right from the start which was unique in PCP. They called me the road-runner as I would often lap the others running around the track.
Also, they put me on double-rations, which was the exact opposite of most of the others in PCP, which were on restricted diets. I got my 3-mile run to about 16 minutes which was around 5 1/2 minutes a mile. Pretty darn fast though not exactly world class.
So push-ups and pull-ups were my weakness in the Marines. I did eventually get up to the maximum 20 pullups but it involved a technique that involved kicking my legs while on the pull-up bar.
I'm just saying that I was in excellent shape and could run circles around most. But those pull-ups and push-ups were not easy.
I had the same issue in the Army. I was 6 foot weight 131 pounds and knew I had issues with push ups. I just made it point to do extra pull ups and push ups through out the day.
When it came to the PT test, I had the fastest run time, but just meet the push up requirements. Did not get recycle because I knew I had it issue with my body build.
Did 22 years in the military, but always had issues with push up. I just work a little harder to make sure I pass my PT test. I still enjoy running and biking, just no upper body strength.
Bench presses are harder for tall folks too even if muscular