Downloading app and writing 12 words is easier than that. Besides, it is more satisfying to teach them to do it the right way.
Discussion
And how will their BTC stack grow from writing down 12 words? An empty wallet is of no use
You can sell them some. Thanks to that they will witness an actual bitcoin transaction.
I would be worried that if you just pass them onto a centralized institution, they will misunderstand what bitcoin is because of it.
Or how would you explain it to them? "Hey, there is this bitcoin technology. But don't use it. Buy IOU from a corporation instead."
I would not waste any KYC-free BTC to train someone. Once they accumulate, they can self-custody their own sats from the corporation. At the end of the day, they would simply be buying from an exchange, as almost all banks can only act as proxies with a simplified UI/UX.
I had success explaining self custody to normies by simple analogy. It's like holding a gold coin vs. having paper gold. After that everyone understands that it's better to hold the real thing. Then they can go and buy from an institution.