Each index.html has a script tag like follows (note relative url and not absolute):
<script src="script.js"></script>
If I visit “myproject.glitch.me/test” (note no trailing slash),
then script script tag in /test/index.html does not resolve to /test/script.js but it instead resolves to /script.js.
If I visit “myproject.glitch.me/test/” (note inclusion of trailing slash), then the script tag resolves to /test/script.js as expected.
I think it would be a better experience for Create a Website style projects if visiting what resolves to a subdirectory without a trailing slash redirected to the trailing slash url to assist with relative paths.