Yes, that’s the general idea. You’ll always be able to use ChoiDujoirNX to switch back to whatever version you started saving fuses at.

I’m not too sure of the real practical application of it though, as I’m not sure how much use the older firmwares will truly be in the future, but anybody who saved their fuses at 4.1.0 and lower for example can switch from using a paper clip to reach RCM to that new software only dejavu/pegascape hack that just came out, and there’s always the chance of a better software only exploit in the future still too. I’m sure it will be dramatically more important for those who own patched RCM switches in the future.

 

Theoretically, you could boot your emuMMC with "stock=1" via CTCaer's Hekate mod, and it should be nearly as good as booting a stock sysMMC the same way. It's not a perfectly unmodified console, so there are still ways that it could be identified, but all the logged data should look completely normal.

Also, I'm not aware of Nintendo doing any special checks to try to identify someone doing such a thing at this point, and the leads in the modding community should be able to identify that sort of thing pretty quick if they decide to start.