If I’m reading the git blame correctly, it looks like it was committed this way in the initial implementation. Based on that, I suspect it wasn’t considered important to include it. You could open an issue requesting the functionality, maybe add a PR with an implementation submitting a patch that implements this functionality.
I’m curious, what do you want the embedded file’s original modification time for?
EDIT: You could probably wrap the embedded fs.FS to implement this yourself with a go:generate command.
Excellent find, thanks. I now understand the rationale behind this design, but this makes the documentation (https://golang.org/pkg/embed/#hdr-File_Systems) misleading. At the very least this justifies a warning. Do you know how to properly report this?