The circuit is by concept slightly different from what Nigel quotes. There is no in-line resistor (probably to deliver the maximum potential to the connector).

When you say 3 plus thermistor, do you mean including the 10K load?

They could have included the 10K into the the internal circuit, so there would be no requirement for an additional resistor externally - historical reasons possibly? Earlier sensors needed it, so now they stick to it?

Edit: Just thought about one more possibility: without the external load, the electronics would be measuring the potential, but without current flow (nA or less). This would make measurement very susceptible to interference from magnetic fields if long sensor leads are used. By adding the requirement for an external load (and planning for it in their internal circuit) it would ensure at least some current flows, hence provide more stabil reading - maybe?

J