it is possible to retrieve a taxa via /v1/taxa/{id} in the API, and the response will include a vision field that tells you whether the taxon is included in the current vision model. here’s an example of a request to look up a couple of taxa (click to view the response): https://api.inaturalist.org/v1/taxa/196822,196823.
the only difficulty here is that you have to specify a list of taxa IDs, rather than searching for, say, all taxa with a particular term or a in a particular genus. to do that kind of search, you have to use /v1/taxa in the API, but the results will not include the vision field. you could request that this be updated to include vision in the results. alternatively, you could get a list of taxa from /v1/taxa (ex. https://api.inaturalist.org/v1/taxa?q=moose&rank=species&per_page=500&only_id=true) and then look those up via /v1/taxa/{id}.
i’m not going to write such code, since i don’t see the benefit in doing something like this, but i have created a page that will present the results of /v1/taxa in a human-friendly format that may or may not be useful: https://jumear.github.io/stirfry/iNatAPIv1_taxa. this other page may also be useful: https://jumear.github.io/stirfry/iNatAPIv1_observations_species_counts?taxon_id=3&order=asc