This design is likely valid for HA with firepower (FTD). The cabling to the ISP-router in the diagram does not really show if both firewalls can share a common subnet, if not you need additional WAN-switches between router and firewalls.
The firewalls don't use HSRP or anything similar, they have a proprietary HA mechanism. Other than with HSRP you need two exactly same firewalls to build a HA system.
