Pass Holder reservations Barcelona - Marseille

I’m new to Eurail so apologies for my knowledge not being up to scratch.

I hold a Eurail 2nd Class Global Pass and looked to make a seat reservation on this route for upcoming July. The Eurail site indicates reservations are not available until 90 days prior yet they seem to already be for sale on Rail Europe website. However the pass is not eligible for the direct route - is this because it is 2nd Class? Can I only use it on the train with a change in Narbonne?

Also, in this situation where seats are for sale but not open to passholders, is there a risk that passholders could miss out on a seat, or are a certain number of seats reserved for passholders.

Thanks!