It is worth setting the expectation in the CheatSheet that WebMCP is in early preview, under active development and the API surface is changing frequently as a result of that, otherwise users of the cheatsheet might be surprised when some of the APIs documented there don't work.
And that's exactly the goal. There's no recommendation against using features that are not in Baseline - and there is a superset of features that are progressive enhancement or polyfilllable, but those are much more use-case dependent - Progressive Enhancement frequently depends on the use case, and Polyfills vary the impact they have on performance, so need more care.
Baseline is being discussed and defined in the WebDX Community Group: https://www.w3.org/community/webdx/. It's not a created by web.dev or Google, but there are people who work on it who are part of the W3C Community Group.
Btw, Web Bluetooth is not only supported by Chrome, but also by Edge, Samsung Internet and others. More on supported browsers on https://caniuse.com/?search=web%20bluetooth
