Some releases are stored as revision in the graph (maybe due to an old bug in the git loader?)
For example, look at
https://archive.softwareheritage.org/api/1/origin/2695882/visit/12/
you will see that only 1.0-rc7 is correctly stored as a release, all the others are, incorrectly, revisions.
"refs/tags/0.9.1": { "target": "45b0039a63c5da3164c6c2c3ff5deabea09ae4ba", "target_type": "revision", "target_url": "/api/1/revision/45b0039a63c5da3164c6c2c3ff5deabea09ae4ba/" }, "refs/tags/0.9.8": { "target": "bfafe56602af035f59dcb6a9bd1ac3d68f193052", "target_type": "revision", "target_url": "/api/1/revision/bfafe56602af035f59dcb6a9bd1ac3d68f193052/" }, "refs/tags/0.9.9": { "target": "d56ae79e43ff1b37534370911c8a78ec7f38d437", "target_type": "revision", "target_url": "/api/1/revision/d56ae79e43ff1b37534370911c8a78ec7f38d437/" }, "refs/tags/1.0-rc1": { "target": "7596fdc31c9aa00aed281ccb026a74cabf2383bb", "target_type": "revision", "target_url": "/api/1/revision/7596fdc31c9aa00aed281ccb026a74cabf2383bb/" }, "refs/tags/1.0-rc2": { "target": "00e81c89c29ff3e58745fdaf7abb68daa1389e85", "target_type": "revision", "target_url": "/api/1/revision/00e81c89c29ff3e58745fdaf7abb68daa1389e85/" }, "refs/tags/1.0-rc4": { "target": "9f1f03ad692f3e98e2c3cb447a54de88e8353b0e", "target_type": "revision", "target_url": "/api/1/revision/9f1f03ad692f3e98e2c3cb447a54de88e8353b0e/" }, "refs/tags/1.0-rc5": { "target": "a7cd1f755cba27f903253c418bdf34bb3962405e", "target_type": "revision", "target_url": "/api/1/revision/a7cd1f755cba27f903253c418bdf34bb3962405e/" }, "refs/tags/1.0-rc6": { "target": "942f90e4ab18c4308a524176f804a88f5ce63454", "target_type": "revision", "target_url": "/api/1/revision/942f90e4ab18c4308a524176f804a88f5ce63454/" }, "refs/tags/1.0-rc7": { "target": "3e7076586691d4e363689fbf5374f833289e0b98", "target_type": "release", "target_url": "/api/1/release/3e7076586691d4e363689fbf5374f833289e0b98/" },