The true effect of this switch will likely happen when installed iOS version is at least one generation older than the currently supported version. That’s when Apple decides to aggressively force upgrades.Thanks both - makes sense.
I do remember getting the annoying ‘install update’ prompt numerous times on my old iPhone 6 which I retired last year when I bought the 11. Strangely though, I don’t get this alert on my 11. I’m still on iOS 13.4 at the moment, haven’t bothered to update it yet. On the software update settings page, there’s a link to ‘download and install’.