Super late here but I got the answer, so essentially battle ratings are used to tell the game how good a vehicle is so it won't match a ww2 tank with a modern one.
BR (Battle Rating) starts from reserve (essentially like 0.7) and then goes 1.0 1.3 1.7 2.0 and so on, The BR of a vehicle can change if the selected mode is Arcade or Realistic and does not matter for simulator battles (usually, else it relies on the Realistic BR)
Your BR is determined by the highest BR vehicle currently in your lineup excluding ones that can't fight in the selected gamemode (tanks if the selected gamemode is air arcade and planes if the selected gamemode is ground arcade)
Once your BR is determined you will enter a fight with players that have a lineup BR (the one determined in the part above) that either equate to yours or slightly deviate from it in a range from 1.0 BR above you (that's called a full uptier) and 1.0 BR under you (that's called a full downtier) anything in between is either a normal uptier or downtier or in case the BR equates to yours it's just a normal match.
Preferably you want to get a full downtier as then you'll face weaker vehicles and usually less experienced players.
Now there are subcategories in Death% for surrendering on different airfields. Landing on an enemy Airfield gets you a unique countdown 'You will be captured in [time]' and a death message of 'Crew surrendered'.
