This is not true 10nm, it would be same as Intel 14nm since Intel counter part is more dense. Oh well...
While that might true, I assume things like voltage, heat dissipation and power consumption are nonetheless positively affected going from 14nm to 10nm even if the transistor density remains the same? So how important is the transistor density metric exactly when it comes to the end user experience? Dare I say, zero importance?
From what I have seen Samsung's 10nm is about 10% denser than Intels 14nm.
The whole nm thing is mostly marketing albeit usually at least some parts do have a "feature size" of that size specified. All sorts of factors like number of fins, fin height, fin pitch, gate length, etc come in to play.
Then of course the manufacturing part is only one piece of the puzzle, the chip design also will impact logic densities since this is also a Samsung chip on the Samsung manufacturing process its worth noting. You know if AMD's old bulldozer chips were made on Intels 14nm they wouldn't all the sudden be Kaby Lake's.
AFAIK the nanometer number as a benchmark for comparison is a bit like the megapixel. I am definitely not qualified in this area, but reviews have led me to believe that if your process node is geared toward power consumption then you get higher transistor density because you can pack those small wires tighter together, but if you want Ghz and quality at higher TDPs you need to space those small wires further apart so that power leakage from the higher voltage doesn't break your chip, and so that that same voltage is actually possible to cool as it isn't all packed into a little space that a sink cannot transmit heat from quickly.
This is why ARM cores clock higher than x86 at the same process node and TDP, but ARM can't get itself to 3ghz so went many-core with its first PC offerings (in servers). ARM cores are specifically designed to be small and efficient. The core itself is just too tiny to cool with heatsinks (unless there's 48 of them warming each other in a server chip) and thus clock higher.
TL DR: Transistor density comes at the cost of heat. ARM are passively cooled so even though they are super low power they chose a process that prefers power efficiency at the cost of lower raw density.