Im guessing this was a partly domestic itinerary?

For some reason the klm and af websites have recently been showing incorrect class of service when booking. I have seen this when the fare basis is a PE one for example, which causes some (though not all) short haul feeder flights to also show PE class of service. Which is not the case as those flights don’t offer a PE cabin. It has to do with the overall fare being a PE one.

If you load your itinerary on the Saudia website it should show you the fare basis and fare code for each segment individually. That may give some clarity as to what’s going on.