If Expedia are happy to sell you the ticket you want to buy, why not buy it from them?

(what's a "NON operational seat"?)

It seems that you are unhappy that KLM won't sell you a flight from GRU-ATL-(wherever)-CWL [Or else, you are unhappy that Delta won't sell you GRU-AMS-CWL all on KLM - it's not really clear, but the same reasoning that follows as presented for KLM applies equally to Delta if instead your complaint is actually about Delta not selling you the KLM tickets you want]. It makes sense that while Delta may want to route you via ATL - because they can put you on two of their own long-distance flights - KLM would instead prefer to put you on GRU-AMS-CWL, thereby avoiding Delta altogether, and thereby avoiding the need for two transfers. Most customers would prefer to have as few flights as needed - a direct flight always being the preferred option - and as few periods of down-time waiting at airports between flights, so it is not surprising that KLM will focus on the faster, more direct options. There is no requirement on you to buy any flights offered from KLM, just as there is no requirement on KLM to offer you every possibility for getting between any two points. If you find the exact itinerary anywhere else - such as on Expedia - then you should buy it there.

Remember, the airlines are not travel agents, and are not in business to provide you with the full suite of possible connections and itineraries. If you want to fly airline A, you should book from airline A or from a third party, rather than expecting airline B to sell you the codeshares it has access to on that other airline. The majority of airlines around the world will only put you on codeshares when they also get to put you on at least one of their own flights - and preferably, the majority of the flights they put you on will be on their own flights, rather than on any codeshare partners. You can't feasibly go to Delta expecting them to sell you tickets for longhaul travel that only include KLM operated flights, just as you can't feasibly go to KLM, expecting them to sell you tickets for longhaul travel that only occur on Delta flights, particularly when there is another option that is more "preferable" to the airline in question, i.e. putting you on their own flights for the majority of the trip.