Hold is different, sights are different, trigger is different, reload is different, complete manual of arms is different. Training on one rifle does not equate to training on all rifles.
Hold is no different. Lining up sights is lining up sights - and most people use an optic anyway. Triggers differ between different AR’s anyway. The differences you cite would also apply to my AR-15 vs. my AR-10. All are so minor as to be inconsequential.