Chain catchers are simply for those who do not trust their mechanics enough to adjust their front derailleur correctly. I would say save your money and find a better tech if your dropping your chain. The front derailleur is the chain catcher and adding an aftermarket piece is not going to the root of the problem.
I've had an awfully experienced and well respected bike mechanic tell me that sometimes you just can't tune it out and that's why the chain catcher was invented. I had been having a problem dialing in my daughter's triple to avoid chain drop given the type of riding and (lack of nuanced) shifting she does. I'm not a pro mechanic, but have always had very good success dialing in FD's and it's not rocket science. Maybe the chain drop could be prevented with better tuning (neither he nor I could) or better shifting (but she shifts like she shifts), but the reality is that she was getting discouraged by the occasional issue on the road in the middle of no where and the chain catcher was an easy fix and made her more likely to ride the bike.
So you may be correct, but probably not. But even if you are, anyone who thinks they live in a world where things can be adjusted perfectly all the time without exception is going to be disappointed. A chain catcher is an elegant (cheap, simple, lightweight) solution to a problem that might be preventable in all cases (I doubt it), but when it happens, at the very least it's a hassle or messy on the road fix. At the worst, it causes an ugly, if not damaging, chain drop. Easy way to deal with an imperfect world.