Pracically, most of the time, IMO, where learning speed matters, is when you're competing against someting, could be an individual, or a startup, etc, which doesn't seem to be the optimal condition one would like to be in.
I'd argue that using calculators instead of learning how addition is done does hurt kids' ability to do mental arithmetic. It's an experiment we haven't tried, or at least not in places I've lived in. Sure, once you get how addition is done, feel free to free up your mind skipping 2+ digit arithmetics using a calculator. Same as: sure, once you learned what caching is and implement a small prototype, feel free to ask Claude to implement caching for you.