Anyone know if they're referring to "accept filters" here? FreeBSD folks can "man accf_http" if they're curious, which does prevent a request from being handed

Anyone know if they're referring to "accept filters" here? FreeBSD folks can "man accf_http" if they're curious, which does prevent a request from being handed off to the application until the complete (and valid?) request has been made. Certainly not a "hack" but a feature of the OS itself.