Well, there is no FAF for a precision approach, the final approach starts at the FAP, which is wherever you happen to be when you start down the glideslope. You are the, by def, on final approach.
USA does have it's own non ICAO method of establishing instrument approach procedures (TERPS vs PANS OPS), but that does not mean that you are "at your own peril" with the glideslope coupled at any time, as long as you are not below the relevant altitude (MSA, intial approach altitude or whatever depending on how far out you are).
Coupled or not, the autopilot is NEVER responisble for terrain separation, you, the pilot, are. GS, VS or whatever descend mode you may be using.