You can go to this link:
https://www.rvtrader.com/Keystone-Sp...1760BH%7C55763 and view photos of about fifty (50) new Springdale 1760BH trailers that are for sale around the country. Some of them do have microwaves, some of those microwaves are "just sitting in the open space", some of them are "installed with a mounting plate around the microwave" and some of the trailers have a "big open space where the microwave would go"....
So, there's no "one rule applies to every microwave in every Springdale 1760BH.
My "guess" would be that in 2022, the microwave may have been an optional item, either installed at the factory (with no mounting plate) or installed at the dealership (could be with or without a mounting plate, depending on the dealer" or sold without the optional microwave.....
Looking at both the 2022 east and west brochures, there is no "standard/optional features" listing. In the 2021 brochures, the microwave is listed as a standard galley feature and it's also listed as a standard feature in the 2023 year models. Why there are several for sale around the country with "open spaces" and some with a mounting plate while some do not have the mounting plate would lead me to believe that during the 2022 model year production, there were some changes made due to appliance availability.
Those "changes without notice" are not usually something Keystone will go back and change under warranty after the sale. It's a "What you buy is what you get" kind of situation.
All that is "addressed by the statement: "All features, floorplans and specifications are subject to change without notice".
Unfortunately, you may find that you have no recourse with Keystone. Possibly, if your dealer installed the microwave after it was delivered to them, they may be able to install a mounting plate for a reasonable price or possibly even as a "customer satisfaction" with no charge. You won't get that kind of service "with vinegar" so keep things "pleasant and civil" if you approach the dealer with that kind of request.