dense valley
I mean Minecraft has the option for singleplayer so I don't see why not be able to use LC offline as well just like the Minecraft launcher allows you to. Currently, I use LC as my main launcher and I have a singleplayer world, I don't have access to the internet on my PC at the moment which directly results in me not being able to access my singleplayer world.
It could work so that if you have logged in and launched a version of the game before, you could have access to singleplayer Minecraft in that version without the internet.
alpine sedge