Trust equivalence section uses terminology that is not well defined
The section reads:
[...]
The equivalence binding is invalidated under the following circumstances:
* if either primary key is hard-revoked.
* if either primary key overrides the equivalence binding with a new direct self-signature that a) does not contain a Replacement Key subpacket, or b) contains a Replacement Key subpacket that does not refer to the other key.
* if either signature that forms the equivalence binding has expired.
Note however:
* If either primary key is soft-revoked or expired, the equivalence binding is unaffected.
* If either primary key is hard-revoked, then the equivalence binding is invalidated and the other key is unaffected.
The notion of hard and soft revocations is (sadly) not defined in RFC9580.
Further, the section uses bound-equivalent twice, that is not defined. I think this term refers to the Key Equivalence Binding introduced in the section, but could be clearer.