Well… you have a point, and you’re kind of proving my point at the same time. Opening Firefox to look things up while booted into sysmaint mode could be a fatal move. You may note that the sysmaint session has no “launch browser” button and no Start Menu - that’s specifically because we’re trying to keep people from launching Firefox in sysmaint mode if at all possible. This does make it harder to look things up, but there’s not any safe way to allow looking things up while in sysmaint mode. (What you could do instead is look up how to do things while in user mode, create plain text files with notes about what you intend to do in sysmaint mode, then reboot into sysmaint mode and do those things. You can access the files saved in your user account by running sudo -i, then cd /home/user.)
Obviously this is going to be severely annoying for a significant number of use cases. And as a developer, I freely admit to using sysmaint mode for things it isn’t designed to be used for (mostly building packages from a VM shared folder). My threat model is such that I can do that safely, but since we’re trying to cater to much stricter threat models, we try to make it harder to shoot yourself in the foot that way. Most users who have a less strict threat model can probably afford to remove user-sysmaint-split. (The only reason I don’t is because I have to develop the sysmaint session itself, so having it around is essential.)