Does a slot swap cause an application to restart when using deployment slot settings?
if both are running 'warmed up' and in 'Always On' mode then the swap would not cause a restart of any kind. But go to this URL and read the point #1 and if any of these things are done then it will restart.
https://docs.microsoft.com/en-us/azure/app-service/deploy-staging-slots#what-happens-during-a-swap