Not necessarily true and for the most part, unenforceable. Here's the "out":
(2) A person is not in violation of the offense described under this section if the person is proceeding in a manner needed for safe operation.

Nothing in 130 requires you to pull over. That's another statuate, 811.425 and again, good luck on enforcement and conviction in court.
The short version: What is safe for you does not mean it is safe for grandpa. Too much left open for interpretation. A lot of courts I worked with before retirement had a general rule they followed, 10 MPH below the posted/designated speed and at least 5 veh's in line behind the offender not including any police vehicles. I won't even start on the experiences in court with this law.
There is also the bottle neck effect. If you get cars at the head of the pack driving 45, the farther you get back down the string of traffic, the slower you go. Good example is Hwy 18 at Fort Hill (MP 25). That 45 zone will turn 18 into a parking lot clear back to Hwy 101. Most commonly to about MP 13 to 16. When you get to the Ft. Hill restaraunt the speed picks up and every thing is fine with no visible reason for the parking lot behind you. Another example was two college kids that did a "protest" of the old 55 law. They got on the freeway, one in each lane and stayed side by side at 55 MPH. In short order they had traffic backed up for miles.
Not familiar enough with Philomath to venture a guess on that parking lot.