Whenever a non-technical salesman (or CS rep) tells me "we can't access your data", I usually smile and take it to mean "I personally don't have access to a GUI for sifting through your data". Not that such an interface it likely to exist at all, but that I don't trust them to know anything more detailed than that.
Right, that's why I think SpiderOak (and preferably the whole industry; Signal, WhatsApp, etc. are in the same boat) having a marketing term for this is important: "our product, if properly implemented, is designed in a way where nobody can build me that GUI" is meaningfully different.
