Reading through that, there are some definitions I think could be done better.
In section 4.2 you have:
Downstream:
In a direct relationship between two ASes the one receiving upstream from the other. (See: [RFC9234], also known as the customer in a customer-provider relationship.)
Upstream:
In a direct relationship between two ASes the one providing upstream to the other. (See: [RFC9234], also known as the provider in a customer-provider relationship.)
Providing Transit:
Forwarding packets destined for addresses in an advertised prefix, while advertising a full BGP table or default route to the neighbor.
Providing Upstream:
See: Providing Transit
Especially with the definition for "Upstream", it took me reading the whole of the section to understand that you don't actually have a circular definition there. If you change the definitions in the "Downstream" and "Upstream" sections to refer to providing or receiving "transit" instead of "upstream" I feel that it would read more clearly as well as pointing to a term has its own definition without pointing to another term.
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Dan