This is wrong.
At a Bio POI, the wave-scanner doesn't detect any of the shards or braintrees etc. It ONLY detects the mat's, themselves.
As you harvest the mat's the signal decays until, at a completely empty site, there is no more signal at all.
At a Geo POI, the wave-scanner simply detects the area, itself.
Even when you've harvested every mat' at a Geo' site, the wave-scanner continues to display a signal.
It's either operating in a deliberately inconsistent manner or it's simply not working correctly.
In either case, it needs fixing.