It's close. Long chain polymer VI improvers coil up and thicken the oil somewhat when hot. (not thicher than when cold, but thicher than they would be without them) If and when these long-chain polymers shear, they loose their ability to stabilize the viscosity.
This is about half of how multigrade oils work. At the other end, pour point depressants keep the oil from thickening as much when cold, and friction modifiers reduce the cold strat friction, reducing the cranking power required to start the cold engine (which is part of the SAE test sequence for the XW part of the rating - so in reality a
10W30 oil is closer to a 15 weight oil with addatives - or even a 20, in the "real world"