When I'm importing fetch-mock (7.3.0) in IE11 I get an error Expected identifier which traces to the line function findStatus(val, { useSTD3ASCIIRules }) which seems to come from 'tr46' dependency.

Since this module is imported as a string in the 'es5/client-bundle.js', webpack can't transpile it correctly (and argument destructuring actually is also not an es5 feature at all).