Back to Basics: The Many Modes of Proxies
I dont think that is correct, the connection table is updated but does not require a SYN packet to do so.
https://support.f5.com/csp/article/K7595
The FastL4 profile determines how the system handles the connection table entries. Enabling the Loose Initiation option allows the system to initialize a connection when it receives any TCP packet, rather than requiring a SYN packet for connection initiation. It also provides a good alternative to the high overhead of connection mirroring. In the event of a failover, with the Loose Initiation option enabled, the standby BIG-IP system accepts connections mid-flow, and forwards, as expected. The Loose Close option allows the system to remove a connection when the system receives the first FIN packet from either the client or the server. This will help trim connection table entries as the connection entry can be removed as soon as the connection officially closes, and the system does not need to maintain the connection table entry.