At endojs/endo#1655 (comment) @zloirock writes

core-js use strict mode, but, for modules size economy, not in all cases - for example, in cases where this depends on it. I didn't think that .arguments and .caller are interesting to anyone. I can consider adding the strict mode in all affected cases. You could open an issue in the core-js repo.

Thanks! This is that issue.

At endojs/endo#1655 (comment) I show the error message from SES initialization

Removing intrinsics.Iterator.from.arguments
  ✘ [fail]: shimmed iterator helpers Error thrown in test
failed to delete intrinsics.Iterator.from.arguments (TypeError#1)

This indicates that the Iterator.from function added by core-js is a sloppy function. I suspect but have not verified that Iterator.from is simply the first encountered of many similar cases.