sorry you had to manage that much troll posts in this thread
I also had that 4.1.0 notification (well, it didn't tell me the version number, just "please update") on the same day, but I had my internet enabled so I didn't find it strange.
What I found strange is the speed it took to update. like, instantly. Like in fact there weren't anything to update or replace.
So, mayyyybe (yeah, supposition so far), the 4.0.1 update had a license issue for something nintendo couldn't use until december, but they embedded it in 4.0.1 anyway and made the console use it and update to version number to 4.1.0 without downloading anything new from the server only past a certain date (the file was already on the console ! waiting to be used until a certain date).
Something like exFat license, or anything else planned that they had to renew ?
it asked me to update before ever inserting an SD Card, so it's not a renew of exFAT license. could be anything else.
What's strange is that it didn't go from 4.0.1 to 4.0.2 for a small fix, but increased the major version to 4.1, it did add something major, but updated quite quickly. Unless file access is very fast now, or the update was only a small file.
for users asking, you could refuse the update and still play the games. it's not a mandatory update.
Like SG854 asked, did you try to update ? (I didn't read anything from you saying you did). or you still don't want to try?
just to see if indeed you already have the needed files, or if it's just a time bomb to a known release date embeded in 4.0.1.
4.0.1 time bomb : I know the release date of 4.1.0 and will prompt you to update, but you'll need a connection to do it.
4.0.1 embedded file : I know the date I need to update a license, and will prompt you to update, you don't need a connection because I already have the needed file !
another cause : it did download it from other means :
- other consoles? it can sync game's update with someone else's switch, it sure can do it with console's update too. it doesn't require a network setup to sync. but your only contact is a non gamer neighbor.
- some communication we don't know? Does the console try to connect to open hotspot like 3DS?
- kept internet info even if deleted? possible, your router should log that. set a proxy to enable switch communication only when you want.
- hdmi communication though internet connected tv (but you said you didn't connect to TV).
I think time bomb and license file update are making the most senses, but other users who didn't power their console since 4.0.1 would have the same update prompt for either both suppositions.
based on LeonMagnus's post above, not having the prompt means its neither time bomb or embedded file, it triggers the prompt only when an update is ready to install.