i'm ok that they built it in polymer& shadow dom v0, with slow polyfills. that they seem unable to escape or improve past that choice is quite lamentable, but i don't understand fully. frankly other browsers should better support v1 by now.
In future, you can always DM me to find out what's up with issues like this. @surma and I are point people for improving compat (as I'm sure you've seen in other instances).
& Web Standards TL; Blink API OWNER
Named PWAs w/
DMs open. Tweets my own; press@google.com for official comms.