Lengthy discussion regarding this can be found here: https://forum.inaturalist.org/t/are-drawings-evidence/8595/1
Personally, I consider drawings valid evidence, though I do acknowledge the problem that details may be misremembered if too much time passes after making the observation. People should also always include only those details that they remember, and shall invent none, even if they are plausible.
Scientists have managed centuries with drawings instead of photos, so I don’t see any reason of tightening the rules for this now.
Lastly, I do think there should be higher standards regarding unusual observations, however. If someone observes a wild rhinoceros in Antarctica, I’d want photo evidence of that!