The Front Desk Manager is wrong.

At Autograph Collection hotels the United States, the Platinum Elite (and above) Welcome Gift is your choice of 1000 points or a USD $10 F&B credit. In comparison, at various Starwood legacy brands and at resorts of various Marriott legacy brand, another Welcome Gift choice is daily breakfast (not just continental breakfast) in the restaurant. It's true that daily breakfast is not a Welcome Gift option at Autograph Collection hotels. There is no reason to refuse the 1000 points or the USD $10 F&B credit. Pick whichever you prefer.

However, that doesn't mean there isn't also a breakfast benefit for Platinum Elite at Autograph Collection hotels. It's just that it's a function of Guaranteed Lounge Access. As already documented in this thread, if there's no lounge or it's closed, the member (not the the hotel) gets a choice of "daily continental breakfast in restaurant for member +1" or "750 Points per night of stay."

Hotels also have the option of being listed in the Terms & Conditions as not giving members this choice, simply providing 1000 points daily instead. Only two Autograph Collection hotels are listed: The Algonquin Hotel Times Square, Autograph Collection and The Lexington Hotel, Autograph Collection. There are also special terms for The Cosmopolitan of Las Vegas, Autograph Collection in the terms & Conditions.

The paragraph above does nor mention Triada Palm Springs, Autograph Collection. That means there are no special rules for this rogue property.

Finally, a 4-star hotel should not consider a muffin and fruit to be an acceptable continental breakfast. A real hotel manager would know that many guests would not he happy with a sugary muffin and would not consider this to be any sort of proper alternative to an executive lounge breakfast at a 4-star hotel. They don't need to provide bacon and eggs, but there should be a choice of healthy and unhealthy (more decadent) breakfast options for various tastes and health needs.