vSphere HA will restart guest VM on the other ESX, when guest VM is down.
Not when Guest VM goes down, When the ESXi host goes down. It restarts all the VM's on another host.
FT will have secondary guest VM on on other ESX,and sync with Primary guest VM, and when Primary guest VM is down , vSphere swithch over to secondary guest VM without almost no downtime.
Perfectly right.