Great posts and I also missed out on the train.
Arm strength for a C is the number #1 focus and I can understand why. Can't teach that. I have a 2016 C-only who is an undersized 16 year old at 5'8", 170 lbs that has been formerly trained since 3rd grade. He looks like a catcher, eats and breaths it, and is a complete wall behind the dish with textbook blocking and incredible lateral quickness, soft hands and a high C IQ. Has impeccable footwork, transfer and throws every ball on the bag. At this point, his POP is 2.15-2.30 with a 68 mph velocity, but he throws a lot of runners out on a high level travel team due to the aforementioned items and ensuring runners are held on closely.
However, he does not usually stand out as a top 5 catcher at showcases or camps or travel tryouts as 95% of the time the only C evaluation is 5-6 throws to 2B to get a POP time (and sometimes a velocity). Watch him catch 2 games.......then the advanced nature of his skill set is appreciated. Nonetheless, the reality is that arm strength/POP time matters big time and he continues to work to improve that.
Although velocity is important, it is about 6/10ths of POPTIME. The other 4/10ths is in the release. Too many camps/ showcases focus on velocity. So, you could select a catcher with superior velocity over the catcher with superior PopTime!!
The true young prospect is the catcher with the mechanics to be accurate and the release time .8 and under. As he gets bigger/ stronger, his work ethic will improve velocity.