Not always. My recently deceased Thinkpad 13 chromebook with an Intel 3855U held up despite lacking support for multithreading. My HP Mini 311 with an N270 played HL2 and CS pretty well for a single core processor (yes, the Nvidia ION helped).

Currently rocking a Lenovo chromebook Flex 5i with an i3-1115G4 and it's outperforming my phone's Snapdragon 845 in rendering video animations by a reasonably well margin.