Thanks for the additional information; so if I'm reading it correctly, it's basically a different format/style of index files?
So far as I can tell, it's been around for quite a while (2016?), but doesn't seem to be widely used or mandatory? I didn't look too deeply.
In any case, supporting one style of Debian index files is already a challenge, since we are reimplementing everything from scratch (and not using their tools). As with many package formats, the "real specs" differ a bit from the docs and can only be discovered by studying the source code and/or behavior of clients. Supporting a second format is a big investment, and doesn't make sense unless there's a compelling need (like clients deprecating old format, etc).
If you're looking to query/manipulate packages, I would suggest checking out pgutil
instead:
https://github.com/Inedo/pgutil
Thanks,
Steve