Hey, I see your point about getting the most value out of time spent practicing. BUT you have to understand that the root of the issue lies much deeper than that. You see it is not ONLY developing a particular 'trick' when you're learning moves in your "bad hand", it's also building strength, flexibility, mind/body connection (mental agility?) that you can then parlay into many, many other moves, hopefully your own original ideas.
Also remember you could apply your logic to any difficult area of flourishing. "Well... it takes a long time to learn springs, and build up the hand strength... springs are just one little aspect of flourishing so I'd rather spend the time perfecting my cuts... the audience doesn't want to see mediocre springs anyways!" See, YES it is more difficult and time consuming to learn some of the more esoteric aspects of card handling, but it is time well spent!!!
besides, If you're learning a cut for the first time using one-hand... what is the other hand doin? it might as well be learning it at the same time!
now, I understand that for some guys that have been practicing like a mofo one-handed for many years, it may seem like a huge barrier to try to learn moves with the other hand, because it's bound to be in worse shape. but don't cheat yourself and be very aware of the real reason you choose not go back to learn with your "bad hand" ... that's why its best to start with it as a beginner .
. for instance doing a move like the pass, it has totally no point in learning it with both hands, but ofcourse that is not really cardistry for that matter. but it is a counter statement to your claim "You should learn EVERY single move in BOTH hands or you are only half good at the move."
I totally disagree with this! You never know what angular situation can come up, and being able to do every move with both hands ensures that you can flow with whatever is happening during your magic, or flourishing. Because now you're thinking on a systems-engineering level... WHAT needs to be done rather than HOW you're going to do it. (not that you can't do that to an extent one-handed, but it's greatly limited) So say you mess up a move, or a spectator doesn't exactly follow instructions, or something throws a monkey wrench into your rigid, very well trained sequence... by having an ambidextrous skill set you're able to 'roll with the punches' much better.
well I'm not doing a very good job of concisely explaining what I mean by this, but if you wait (could be a long time) till I get more skilled and more time to think about it , I will go in depth on this concept in general another time.
PS try a "fakie" WERM some time it can tend to blow your circuits. remember stuff like even trying a new way of brushing your teeth with the opposite hand has been proven to help prevent alzheimers... the benefits go on and on!
