Interesting in theory, but try DOING that with an actual Bitcoin client. I've yet to see one that will let you spend Bitcoin from unconfirmed transactions, and IME they generally require multiple confirmations before they allow you to then move that Bitcoin on down the line.
I think you've been using old or uncommon clients or wallets apps then.
Bitcoin Core, which I keep updated.
There's absolutely nothing theoretical about this. Both Mycelium and Breadwallet, the two most popular (and best, imho) wallets on Android and iOS
Never heard of either, probably because I don't pay Apple inflated pricing and have no interest in anything that runs Android.
I did the maths for you, the probability of having to wait an hour for a confirmation is extremely small, having to wait two hours is astronomically small.
Given how long I've SEEN it take for confirmations sometimes, wherever that "math" came from appears to have at least one seriously flawed assumption involved.