The map only shows a single pin even if there are multiple observations, see feature request here: https://forum.inaturalist.org/t/indicate-overlapping-observations-for-map-pins/18406
Both observations are on the map, but if you click the pin, you’ll only get the leafminer. You can still see the plant in the list on the right, and if you hover over it, the bubble will show up by the pin.
Can you link any specific observations that you think should be there but aren’t? In your screen shot, the Eutrochium has too large a radius, and the Scorzoneroides was placed over at Knox Town Hall, not the wetland.