Comment 1 for bug 1876451

In my opinion such URL (without architecture) makes sense only for packages that are architecture-independent ("all").
Arch-independent packages in the distant past have been built on i386 builders, and now (I guess at least since xenial) are packaged on amd64. I assume that due to this history when omitting the architecture in the URL, the i386 version is displayed. See e.g. https://packages.ubuntu.com/xenial/totem-plugins/filelist which shows "i386" in the header.
Maybe URLs without architecture should be marked as wrong with some different error message except for arch-independent packages.