Here is the issue on the tracker (reported on 24th May):
Volcanism related surface deposits (Piceous Cobble, Crystalline Fragments, Crystalline Cluster, Needle Crystals) found concentrated around geological phenomena are bugged on Odyssey. You'll always get tier 1 materials, and it'll be same material over and over. Horizons is fine; if you need raw materials, and going to farm these deposits, boot in Horizons.
Also, I'm a noob when it comes to scanning, so please correct me if I'm wrong, but I think the DSS is little bit broken in Odyssey, too. The filters to swap between geological phenomena for example, doesn't show the results properly; it all looks blue everywhere for me. Or, I don't know how to use it. Booting in Horizons however, my left panel was full of geological signals.
In any case, for the first reason alone, use Horizons to farm volcanism related surface deposits.