Is Hosted Data Layer compatible with First Party Domains?

[UnknownJ]

If I attempt to access:

https://subdomain.firstpartydomain.tld/dle/account/profile/key.js

It returns the standard double-slash comment that you get with any DLE calls for which there's no corresponding lookup, which gives the impression that DLE in general is supported, but offering up account / profile / key combinations that exist on tags.tiqcdn.com still produces the empty output. Attempting other paths (e.g. removing account, in the same way that utag delivery uses) doesn't appear to work either.

Is there a trick to it, or is it just not supported yet?