No, it's because they made it so that while the server is talking the database the entire game freeze's. Then it has to catch up when it gets back, causing fuckery. If you repeatedly set the damage of a vehicle +0.1 and then -0.1 you should lag a server pritty hard without any effort.
Their database is actually a ~200 meg file that is continually appended whenever somebody adds something. Additionally, characters aren't stored by actual player ID but by an internal character designation; which, again, has its own table translating Arma player ID to character ID. So whenever you enter or disconnect from a server (or die), you get your info added again.
Yep. Great database architecture there.
Side note, unlike the older vehicle spawn list which had about 10 different possible sets to use, they were horrendously lazy and set all newer vehicles to spawn in the same location. On every server.