not exactly , its little more complicated
VAC ban = you cant play anymore the game use this engine in any Vac secured server
exempl : if you got VAC ban from CSGO, you cant no more play CSS , but you still can play Team Fortress 2 or Dota.
in same way, you cant play in VAC secured server but if the game have other server you can play on them.
if i have correct, L4D2 use both, VAC secured server and No VAC secured server. if you get VAC ban from L4D2 you still can play it on non secured VAC server (those server can have other cheater or simply high modding shit on server , also risk of HAck tool that can hack your account, but depend of server, some are very trusted)
of course i not recommend you to get VAC ban or dont even try. better to stay on VAC secured steam server ^^