I have made the same observation, it seems to be an institutialized practice across the sectors. They broadcast an alert but the talk is so fast that even with good strong reception it is unintelligible . I wonder why they bother at all as it ends up just being a disservice and a waste of time and effort. If they are trying to minimize the time on the air they are failing badly as the time used was totally wasted. Take a few more seconds and properly convey the message. I rarely have problems understanding talk on the VHF but always have problems understanding the Securite' alerts, you tell me where fault lies. The USCG needs to revise their protocols and performance on these alerts.
I think part of the problem is that they apparently record the announcement and then broadcast it over the VHF radio at regular intervals. The recording may sound OK in the office, at least intelligible, but does not transmit well over the radio. Somehow I doubt they ever listen to the actual broadcast themselves. I've also noticed that CG folks sometimes lack geographic knowledge of their area, as well as details about the weather zones. For example, Santa Cruz Island borders three weather zones; so there is no such thing, really, as
a zonal weather report for Santa Cruz Island. For you, it would depend upon which zone you happened to be in. The "moniker" or description of the zone mentions Santa Cruz Island in only one of the three, so that's the one you get (twice) if you mention you're at Santa Cruz Island, etc.