It's actually not a bad approach. I'll grant that it's one thing if you're talking about a guy like Schwarber who has the kind of bat that will play anywhere, who was not seriously considered a catcher when drafted, and would have been worth the #4 overall pick even if he were a 1B/OF, but catchers are just...weird.
I've been amateurishly following Cubs prospects for 20+ years now and, while I have a vague grasp on a lot of other stuff, catching development has just been a complete enigma for me to understand. It's the one position that doesn't make much sense to me because there are so many variables that go into the position, because catchers tend to be complete weirdos compared to other positions on the diamond (in a good way, usually), and because even the freaking rules applicable to catchers seem to be constantly evolving. I can't even tell you what the Cubs' model is when it comes to developing catchers other than "middling dude who's old for A-ball starts hitting the holy crap out of the ball," and it seems to work! It's why someone like Owen Ayers is both a complete shock to me and also completely unsurprising, because *of course* an older 19th round catcher would do something like this!
Occasionally you see a high draft pick at catcher work out, but yeah, maybe there's something to that approach that's worked for the Cubs.