Some comments on the outstanding issues:

For ECMAScript, I think "match" is a fine choice of verb and is consistent. For the closest comparison, regex 'match' isn't boolean. Regex 'match' returns an array of the matched data - data which may be either detail about a single match OR a list of all full matches depending on whether the regex has a global flag. Regex uses the verb 'test' for the boolean matching.

I think there's some confusion here about what is requested and what you think is requested. What I personally mean when I want to have a way to ask for all nodes in a NodeList that matches a selector or all nodes in an element's subtree that matches a selector doesn't effect the scope of the selectors. For example:

<doc> /.../ <elm1> <elm2 xml:id="bleh"> <elm3/> <elm3/> <elm2> </elm1> /.../ </doc>

var selectorMatches=document.getElementById('bleh').matchAll(':root elm3',resolver);

This selectorMatches variable would be StaticNodeList of both nodes in the subtree below #bleh that match the selector. It would not at all affect the scoping of the selector (':root' still matches the 'doc' element, for example). It would only affect a single thing: it would ask for matches in a subtree of the document instead of all matches in the entire document tree.

At least one issue more that I think should be added:

Currently you can ask "gimme all matches in the document against this selector" but you can't ask "I've got this element handle (from event.target or whereever). Does this very element match this selector?". Even if you did add 'match' and 'matchAll' on the Element interface, those don't make it any easier to get an answer to that question. So, some type of equivalent to regex.test(string) would be immensely useful.