You are not alone and in many places you would be correct. Road rules can vary in small but significant ways from State to State and people naturally just follow what they were taught/told although the rule where they now live is different. In both Oregon and California you would be correct and I would get a ticket. Here is nice breakdown of the issue that Puget Sound Public Safety put out a few years ago:

YELLOW LIGHT: What does a steady yellow light mean in a traffic control signal in Washington? The law (RCW 46.61.055) says that a driver facing a steady yellow light is hereby warned that the green light is being terminated or that the red light will immediately follow which is when traffic shall not enter the intersection. You can enter the intersection when the light is Yellow but you cannot enter the intersection after the light turns red.

Washington, like 37 other states with “permissive yellow” rules, drivers can legally enter an intersection during the entire yellow interval, and a violation occurs if a driver enters the intersection after the onset of red. In the other states that have a “restrictive yellow” rule, drivers can neither enter nor be in the intersection on a red, and a violation occurs if a driver has not cleared the intersection after the onset of red.

How long a yellow light remains steady is depended upon the speed limit of the road. In a yellow light study done in Seattle the average light was 3.5 seconds. The Federal Highway Administration recommends the following yellow light times:

25 MPH - - 3.0 Seconds 30 MPH - - 3.5 Seconds

35 MPH - - 4.0 Seconds 40 MPH - - 4.5 Seconds

45 MPH - - 5.0 Seconds 50 MPH - - 5.5 Seconds

55 MPH - - 6.0 Seconds