One can always self select to spin slower but one has to train to spin faster - my second cycling coach.
For me, leg speed is about practice and heart rate begins to close the spread between slower and faster cadence with training. So HR is not a great way for me to deduce any conclusions about anything other than at some point, I run out of heartbeats which means I have maxed out blood flow to muscles.
The calve muscles act like a second heart pumping blood back to the heart such that there is a relationship between heart rate and leg cadence and and therefore and optimized leg speed - current cycling coach.
The above seems to work for long duration constant power efforts such as time trials and longer duration hill climbs.
I am a current road racer and trackie. I was at the track last night in LA, Carson indoor track working out. The trend in track racing is bigger gears. So if you come to the track as a high cadence spinner, you are going to be directed to gear up. Why? It has proven to be faster. So watching really fast sprinters in LA, they legs seem much slower and the look slower due to slower leg speed but are going very fast.
Generally, power lifters turned trackies are ideal candidates for larger gears and adapt easily.
It is not surprising that you are good out of the saddle where you can engage more muscle fiber and make it feel like a lift. Having said that, those muscles are trainable to faster contractions if you apply yourself.
What seems to be missing is the climb time for the hills in the ride. Going up the GRM is completely different from a 2 minute power climb. What climbs are you talking about? If you are climbing the GMR standing and beating all the other riders, just declare victory! Do not change a thing.