payswarm ontologies

Reading the latest spec, I see the ontology is located at, for example:

https://w3id.org/commerce#Transaction

However the w3id.org website is a directory, rather than, a file

https://github.com/perma-id/w3id.org

I was just wondering if this was intentional or one or the other is
preferred.

PS: Danbri sometimes says that it's an advantage to keep namespace URLs as
short as possible ( e.g. ogp.me )