By the word 'true' I assume you mean ones that are not selling on ebay mate lol.
To be honest I seriously doubt if that is something the support team would be able to guarantee unfortunately. The problem is a lot of suppliers off-brand, trade under a different ebay id to that of their business name, especially drop shippers!
They will do their best to hide their business identity to save their DS customers knowing that they are not only selling to them, but then competing against them as well.
It's a situation that you currently find yourself in. Imagine a supplier coping the same sort of flack from 300 a day lol, not a pleasant thought for them at all, so for the most part, their competition against their own customers will be done by stealth.
These guys are there to make dollars, and most will chase down every avenue they can to do it. They will offer sellers a drop ship service as part of that strategy, then go straight out and under sell to increase their sales.
I can't personally see how drop shipping can ever survive in a marketplace such as ebay. Evolution will see the drop ship suppliers cut their sellers loose and take over the market themselves, then go head to head on a wholesale price structure with other sellers.
Sure, there will always be room for smaller sellers who have found markets that the big guys don't consider viable enough for the effort required to sell to that market, but for the most part it will become a big business dumping ground.
It's all a bit dark and gloomy lol, and I don't know how long that will take to evolve, but I do know it's coming. If you chart the business model that ebay offers and the way the online market in general is evolving, it's a sure thing in my opinion!