In practice lots of skills seem to be gained tacitly-- in fact, I would say this is the default skill acquisition process.

Well, I think that at this point we're venturing into the land of "it depends". I would say that if you have "tacit" skills but the wrong map, you might instrumentally do well within the narrow domain where your misunderstood skills work, but you have a chance for a catastrophic failure once you venture outside of it. For example, you could perfectly well do some restricted thermodynamics using the idea of phlogiston. Or you can do astronomy on the basis of Ptolemaic epicycles. Both would work for certain kinds of problems but both would also fail once you try to expand.

And, seems to me, in most cases there is no trade-off and epistemic and instrumental rationality match each other -- the process of discovering the shortest way from A to B simultaneously improves your map.