The Simultaneous Release applies only to Privileged Access users; from the TPAM Administration Guide:
Simultaneous Privileged Access Release
This option allows an Admin or a PPM ISA to grant more than
one Privileged Access User (PAC) to request and retrieve a
password/session during the same or overlapping time period.
NOTE: If another Requestor already has the password checked
out the Privileged Access users must wait for that release
window to expire before they can gain access.