Gregory's Server@yoz it's possible, but...
1) When I tested the 20 sites in IE 11, all of the ones I tested had numerous script parse errors for the same URLs that I saw in my query results.
2) Even if a site were doing this, the fact that they were serving ES5 helper code to Chrome UAs is still not optimal.
@philipwalton Thank you, #1 is what I was looking for. You mention this in a paragraph in the blog post, but the phrasing leaves it slightly ambiguous about whether what you did in IE11 was browse the sites *or* load the Chrome-served code bundles. (Sorry if that sounds kind of nonsensical.)