Load balancing decision

Well, in a sense they do, but maybe not the same way you are thinking of. Remember all monitors are a "ask" and "answer" type function, so somewhere in the F5 there is something waiting for the "answer".

If the monitor is a ping (ICMP), the something knows that the request has been sent and it waiting for an answer. There is a timeout for that specific answer. I'm not sure what the timeout is on each individual ICMP request is.

If the monitor is a HTTP request, they you have multiple levels of "status" that the F5 code could be checking. You have the TCP connection status. The F5 code could be checking to see if the 3-way handshake has completed. Then you have the actual HTTP GET/RESPONSE. Again, at some level something in the F5 knows that the GET has been issued and is waiting for the response.

So, something knows the status of each monitor check, it just a question of how the F5 is using that information.