No, the users need to be able to check for conformance. What we also need is for vendors to supply test platforms. Amazon, to its small credit, does this, which is good, because the subset of html/css they support is limited and poorly documented. Heck, I'd be happy if Apple, Kobo, and everyone else just kept good documentation and up to date!

Though these days I have to spend more time worrying about EAA and ADA compliance than anything else.

A compatibility linter is a poor substitute for a vendor-supplied test platform, but if the vendor is uncooperative it may be the best that can be done.