I would be proud to call that engine mine. You've been ripped off. You need a new mechanic.
I agree with the majority here; and I don't group think or play well with others. By profession, I am Quality Control and paid for my opinion, but not on this site. Nevertheless, I speak my mind. I'm NOT familiar with the particulars of maintenance on your specific engine, but it doesn't take a rocket scientist to call sludge/no sludge. Your engine internals look clean, perhaps even exemplary. Nothing wrong except your mechanic. The ONLY thing I might do different than you is I would print your pictures, show them to the mechanic who told you it was sludged and ask him what he has to say for himself? Preferably in front of other customers.
Sleep well tonight friend!!