The keygen feature has been deprecated. It's likely edge will support more open formats in the future: http://blogs.windows.com/msedg..., including opus+vorbis.
Between firefox, chrome and edge, I'd suggest that today it is chrome that has the greatest support for non-standard features, tracing back to the hastily designed extensions to webkit for the early iphones. In particular many non standard things like speed synthesis and recognition are only on in blink/webkit, as is WebSQL (which, to be fair, was at least once proposed as a standard, even though it was rejected). Those three features alone account for a 15 point headstart (17 if you count keygen) that chrome has over edge+firefox, even though their support should if anything, decrease the score.
It's no coincidence than non-webkit browsers started supporting -webkit- prefixed css properties - webkit has included a large amount of non-standard extensions over the years. Edge's declared preference for feature toggles (and firefox I believe prefers those too, exposing speech api's only if an about:config flag is set for instance) is friendlier to standardization because it means that non-standard features do not become entrenched and hard to fix.
If anything, a high score in html5test means a non-standard browser. Just take a look at the actual features where the major browsers differ and that amount to chrome's advantage - almost all of them are experimental, entirely non-standard, deprecated, or rejected. Why exactly should that count as standards compliant?