Agreed. If the motherboard manufacturer (or notebook manufacturer) says that 16GB is the maximum, then usually THAT is the maximum. I have several Xeon X3400 series servers, and those are spec'd at a max of 32GB. However, the mobo's they're in (one being an ASUS P7F7-E WS workstation motherboard) list maximum RAM of 16GB in spite of having 6 DIMM slots.
Max ram in general is determined by the MOTHERBOARD.