Hi - I don't understand why one would have to be ambidextrous to use them with their left hand. I'm surely not. I will also say that I found in class that the speed strips may be slightly slower than speed loaders, but under stress I had a much higher tendency to drop rounds when using a speed loader.
I could never get used to switching hands. Further, there are a lot of problems with reaching through the frame like that to reload, one being the position of the firearm and your hands, another being the fact that the forcing cone may well burn you depending on loads and how many rounds were fired.
In every case of reloading, one must use both hands, unless practicing some sort of emergency one-handed reloading technique, so there's no reason one can't "teach" their left hand to reload a revolver any more than there's a reason they can't teach it to load an auto.