[What's my assignment] I like this idea, but does it actually get used in Tribes?
Newbies rarely know to use it. It's used by many of the more experienced players in situations like: you joined a server midgame and don't know whats roles need filled. Or you balance uneven game by switching teams, and need to know what the new team needs to win. Or you see a friend on flagstand, and want to ask "you want company/are you gonna handle defense by yourself or need support/should i go attack".
But to be honest it's used more for VGS chaining, like "What's my Shazbot?"
What sort of situations use global sorry?
In tribes there are all kinds of gentleman rules (depends who you play against etc) in regards to melee vs explosives vs chain, or capping out an unbalanced game. It's kinda complicated but often good to have, especially between friends. I guess it remains to be seen if and what things AoT is gonna have that are considered "bad sport" or cheesy tactics. Also teaching situations and such, if you accidentally shoot your mentor or smth.
"I don't know" and "wait" didn't seem worth putting in. They get a lot of use in Tribes?
"I don't know" is usually response to an actually typed question. Or less importantly a humble response to a "You rock" or "Great shot" compliment. It's used a lot in both contexts. Also votekicks and stuff, it's like "please elaborate why exactly this person should be kicked"
Team wait is used somewhat often to attack in sync together with someone, or to say "don't return the flag yet it's in safe spot" ("our flag is secure" is similar meaning). Or "give me the flag but wait for me to regen health first".
Global wait is kinda rare, just used in special honour dueling or teaching stuff.
Attack/Defend sections are requests like "Capture the enemy flag!," Self section is stuff like "I'm going for the flag" -- or did you want something different?
Not really familiar enough with the nyances of pub CTF strategies in AoT versus Tribes to have an opinion on this. 5vs5 may be more straightforward. Generic attack command in tribes is generally a request to "disturb their defense so i can crab the flag", or "we have too many ppl on defense, someone go offense", they are used a lot.
Talking about tribes pubs, how much the actually useful commands (instead of spam) are used depends how good/intense the game is. Some games just have toxic people or folks are just fooling around, or spamming vgs. But when the planets align it's great when people actually play semi-seriously and also coordinate stuff through vgs. Almost always it's used to coordinate who gets to grab the flag and when, as that's a big deal and common source in anxiety in tribes. The other commands maybe less often, but most experienced players know and can use them if they believe someone actually listens.
In any case I think it's helpful to newbies, when they can listen the various requests and communications. Helps build game sense.
On pubs it's of course a mixed experience and some people are more fluid with "VGS language" than others. But the use of gs have grown to be very nyanced with elaborate meanings, and the community has come up with many different contextual meanings for the limited vocabulary available through VGS. I think that's a testament to the fact it is quite useful and often used.
Basic stuff like "Incoming hostile" with the response "Target destroyed" are used all the time. "The enemy is in disarray" is used all the time to tell their defense is broken and someone should snatch their flag asap. "VSAF I go for the enemy flag" means you plan to get it or start a route, while "VFF" means "i'm really going to grab it in 10 seconds or so, disturb their defense, and don't you dare to grab it cause the flag is mine, unless we need an emergency grab to prevent enemy scoring". "I will attack, Wait wait wait" can be used to tell "try to delay your route, I need time to clear their defense". "VCC Completed" when it's done. "VVS Sorry VCD Declined" or such can be used to tell "well I messed up the route and don't actually have the flag, so anyone is free to grab". and so on
EDIT: I guess what I'm saying with this wall of text is, VGS is quite flexible when there are enough commands to work with.