When URI1 redirects to URI2, getResource(URI1) follows the redirect, but seems to parse the content retrieved from URI2 with URI1 as the base URI, which IMO is incorrect (at least, if I judge from how browsers are interpreting relative URLs after a redirect).
The url read-only property of the Response interface contains the URL of the response. The value of the url property will be the final URL obtained after any redirects.
When URI1 redirects to URI2, getResource(URI1) follows the redirect, but seems to parse the content retrieved from URI2 with URI1 as the base URI, which IMO is incorrect (at least, if I judge from how browsers are interpreting relative URLs after a redirect).