Honestly, the thing that I notice is that spawnkilling is actually the most common when one team leaves an entire side of the map open, allowing the other team to just drive through it.
One of the most common examples I experience is on Seversk 13. The most common thing to happen is that like 90% of both teams actually all drive to C. Some maybe split off to B, and usually A is largely devoid of players, sometimes only 2-3 tanks per team fight over it, and surprisingly often you’ll find NO ONE from one team has gone there.
As someone who spawns exclusively at A on that map, its not an uncommon occurrence for me to go and cap that point completely unopposed at the start of the game, and then if my team has also gained B, I can just… Do whatever. Theres no one to stop me. So often I can just go drive up onto the middle road on the enemy side, and easily snipe into the enemy spawn on C side. This stops the enemy team from being able to effectively challenge both C and B, and even if they spawn on A again to try and stop me, Im normally in an already strong position that makes it hard for them to counter me there, because no one bothered to initially defend it.
But by doing this I am effectively spawncamping, however, especially if my team already has B, I have no reason to move. I still need to be there to hold A, and there is zero reason for me to move from a strong position that is denying the enemy ground, for me to drive into a weaker position that is usually unneeded (since with my ground denial it often prevents enemy backup from holding C and gives my team an easier time of taking that point as well)
Seversk 13 is by far not the only map where this is happens, you can do this on many maps. Its most common on maps where one half of it is a town or city or other close quarters area, and the other part is more open fields or hills and stuff. Most people just like driving into the town and brawling, and often leave those outer field flanks severely undefended even when theres a cap point out there.
If you want to prevent being spawncamped, more people need to spawn more often on those sides of the maps and actually defend them. And honestly more often than not those flanks provide some of the best map control and opportunities to flex around the map and control other areas than the cities do, even before you get to the point of spawncamping.