They are allowed on the site for sure. They can’t reach research grade status, at least if properly marked in the DQA with the no recent evidence flag you note.
The iNat taxonomy does contain extinct things - https://www.inaturalist.org/taxa/2713-Raphus-cucullatus
You should however note that no attempt has been made outside of a few areas to fully populate the species, so there is no guarantee something will be there.