From my (still limited) understanding of Polymer, it would appear the beveragebuddy starter uses a deprecated feature for styling. I suspect the other starters do as well. The feature is stated to be removed in March 2018.
https://github.com/TakayoshiKochi/deprecate-style-in-html-imports/blob/master/README.md
Yeah, this is a well-known issue for us as well. Not to worry, though, all features still work as expected and
Polymer has already fixed this issue
on their side.
The deprecation warning is still there, even with the fix. We should get an
update
soon that we can use to make the warning go away as well.