Webarchive is deprecated (Apple deprecates WebArchives - what does this mean for DEVONthink?) and not widely supported. Meaning that apparently the only browser you can use to display them is Safari.
If you want to capture an HTML page frozen at the moment you saw it, my best bet would be a portable format like PDF. Especially if (from your quote) images in Webarchives are downloaded again when the computer you’re viewing them on is online (what a weird concept of “archive”). Which would against the whole idea of having a frozen copy of the page.