the video doesn’t need to be watched unless you want evidence
but it’s easy to check yourself too…. just go check any story-related ‘generic’ character you can recruit like Silent Mastodon, Silent Basilisk, Panzer Buffalo… Gray Mongoose.
you could keep track of any DD recruit but it’s probably fastest to just go recheck one of those set characters so their name/portrait/languages are static (exact same for every player, every file).
and if you go back much later ?
they’ll have learned other languages
kinda a cool detail showing how DD soldiers grow together at Mother Base
but mechanically, also a big deal if you take your time and put in a LOT of hours after you’ve reached Africa but don’t finish all the missions there
as quickly you’ll have so many soldiers that speak all the languages