the muscle doesnt know whether its pressing or extending..and squeezing at the top/bottom makes no difference.
when you do a new movement it always feels like "it really works"..cos its different.
do some research on how muscles work and how the mechanics of the body works also so you can determine what is good and bad advice and what is just pointless advice.
recommending just cables is pointless advice, for instance.
its coincidental that you benefit from it because its a better fit to your mechanical layout.
for others the reverse would be true.
actually your pretty damn wrong,,,on alot of things look at mesomoprhs triceps you want triceps like you do his routine,,,to get them the triceps knows whats going on your mind tells teh muscle whats going on,,,mesomoprh know sthis if you want larry scott triceps you do his stuff to get them,,,,,,the tricep knows if you do presdown, jdm, etc,,,hence thats why everyones triceps are different,,,,I promise you that you follow mesmoprhs routein you will get triceps like his,,,why else would mesomoprh is asking questions on routines to see what others triceps look like so he can get the same look,,,,,if he hates his triceps.