What is going on?

That just means that they are above 100.
After the new update there will be more than 100 lvls.
You can see their ranks in-game.

I think they just own a BF4 server and boost eachother?, for example their winrates - longest headshots and multiplayer score are quite similar.

Wild guesses though

Epic,they got reset.

They got reset,they still boost though.

This guy shows his reports.
Progression - VEi1Side - Battlelog / Battlefield 4
He boosts with those 2 above.
They end the round approximately every 30-40 seconds with the admin tools.
They got a server called i3D.net - CN - #32 that doesn't show up when you search for it.
If you click on the report and want to see the server,it links to another server called i3D.net - CN - #4 which doesn't end the round every 30-40 seconds.
Anybody know such a server where they end the round every 30-40 seconds?

Not sure what they've been doing, but look at their vehicles record. One of them has everything unlocked with just 1 kill and 12m of usage

So why do they get a shitton of XP if the rounds end after 30-40 seconds?

Would like to know that too, seems to be a great way to get some extra exp

And yes it must be something about the short rounds, check their MVP ribbons and Best Squad Ribbons.
But I am not sure if it can be that simple, just finishing a round every minute.

They end the match so fast because everytime they pre-set how many points a team will have in the beginning and it seems that they set one team to the lowest you can ... after 30-40 sec the second team wins and the wining team gets a Conquest ribbon and after 50 of them you get a Conquest medal which gives you a shitton of XP.

Yep,they don't learn.