Why are my observations being set to casual grade for seemingly no reason?

I’m wondering why these observations are being set to casual grade?
They seem perfectly legit to me, and I find tons of observations like them that become research grade. I’ve noticed some correlation between species that are introduced/feral and observations that get set to casual, but if I’m not wrong introduced species don’t need to be set as casual.
here are some examples:
https://www.inaturalist.org/observations/72394712
https://www.inaturalist.org/observations/72316234
https://www.inaturalist.org/observations/71454445
https://www.inaturalist.org/observations/58247140