At best you learn some basic formatting and table calculations, there’s no need to get specific into MS word/excel. There’s essentially no difference between MS and Libre office here. Same with the operating system, if you’re just sitting in an office, reading and answering emails in a browser you don’t have to care about the OS.
Besides, school should teach critical thinking and how to transfer skills, not shoehorn pupils into specific roles and software.
It’s not a question if encryption fails, but when. Paper ballots are anonymous by design, unless you mark the ballots they are untraceable. Digital ballots don’t have that feature.