General policy on hacking is and always has been if you hack you lose online. Anything you get before they realise and bring down the hammer is just a bonus. Some cling to ideas that if you stand on one leg and whistle she'll be coming round the mountain, or hacker equivalent thereof, that you might stay online, and indeed you might get a tiny bit more time than someone more flagrant. Those advocating for such things reminds me more of the skinner box pigeons though -- it was noted that the pigeon in a box with a button that randomly distributes food will get obsessed and do the action that led to the food being released last time even if it has no bearing, that or the car allergic to vanilla ice cream thought exercise
https://kepner-tregoe.com/blogs/hel...a-study-in-problem-solving-the-complete-case/ .
Some circumvent it by playing offline or creating their own online services (easier said than done a lot of the time, especially since local LAN play has died a death.
https://gbatemp.net/threads/private-servers-for-online-gaming.511311/#post-8144717 ).
Detection happens in one of three broad ways.
1) Console level detection of hacks. That is to say the firmware itself has or gains tells and the company chooses to act on them (usually about the time they want more sales, see timing of 360 banwaves). Nintendo have stepped up their game from consoles past as well, and I still never see a proper analysis of changes between versions (never mind a proper deep dive) to say nothing of Nintendo being able to trivially make analysis by such peeps monstrously difficult if they actually cared. I don't know what we have by way of scrubbing identifying marks from things either, though that poses other problems for online play as access is tied to such things.
Dodging this is why people say keep a clean thing for online purposes as outside of Nintendo trying to do some kind of distributed wireless snitching (streetpass back on the 3ds was a kind of take on this, Apple's little tag things are a more applied version that use other idevice zombies to do the tracking -- did see an amusing picture the other day from someone that left a headphone in the middle east somewhere and the other was back in the US) such that your Switch dobs you in when you pass another Switch that may eventually speak to the mothership then what happens offline stays offline, at least until you try to copy saves across and that brings us to
2) Impossible game results. There might be functionally no way in normal play (or normal play for the time count, or normal play since last save backup*) to achieve certain positions, items held, results, stats or similar. Massively subjective and game dependent, even more so if some kind of glitch play or emergent gameplay loop not anticipated by the devs appears, though some things are more obvious than others.
*pokemon in days of old was noted as having two save slots that it alternated between, ostensibly as a backup. If the 2 hours since last save offers a point of comparison then what might be a legal/achievable result from some considerable amount of play might not have happened in the 2 hours. As a lot of saves get uploaded to cloudy services (in this case a server Nintendo control as well -- the someone else's computer was never more apt it seems) these days then there is also that.
I am not sure whether this is 1) or 2) but them banning people that played games ahead of street date would be an example of things as well.
3) Internal validation of results and integrity checks. This is your classic anti cheat -- have money but also have the 9999-money somewhere else mirroring it that the basic cheat maker would not detect. Also things like hashing the whole binary to detect modifications there (principle going back to the 8-16 bit era -- what did you think master codes were, at least some of the time, plus it is also associated with saves going back further still).
This would most likely be what gets you here if there are any (and they can be as subtle as any anti piracy thing you might have heard of).
https://www.theregister.com/2020/01/06/linux_ea_boycott/ being one such example of such a thing in relatively recent times albeit for PC. They say it is to avoid various people doing colour changing tactics (no more camouflage) as a cheat but eh and still serves as an example.
That said as far as Nintendo doing this in anger, much less for something as banal as Animal Crossing, then evidence is a bit more scant. Nobody worth listening to will give you any empathy if Nintendo do decide to switch up their general approach though -- I refer back to "you hack, you lose online" and Nintendo is probably in need of shifting some units about now as they don't have much to shift systems this year/have not had a great year.
