Oregon uses a sign similar to a "Divided Highway Ahead" sign to indicate a no passing zone, except the barrier in the sign is a cross hatch like this. (I've looked for confirmation in the latest Oregon Driver's Manual, but they didn't mention it. Maybe they're phasing it out.) However, at least a couple of times they've gotten careless and used a regular Divided Highway Ahead sign when there is no divided highway ahead.
I drive that highway regularly, the crosshatch sign is just an oddly designed Divided Highway sign that's being phased out (they're replacing a lot of old signs on the highway and that's one of them).
Here's one with a poorly designed crosshatch - no passing lanes anywhere nearby, but if you go a bit forward there's a turning lane.
The first one you linked is an old picture taken a few years ago (I can tell because there's no sign for the market ahead), that sign has since been taken down and replaced with a normal Divided Highway sign. The second one has a center turning lane ahead, but it's over 1800 feet away - whoever placed the sign did a terrible job and should have placed it at least 1000 feet ahead.
The actual "no passing zone" sign is a bit further up on the first link - it's a giant version of the white "DO NOT PASS" sign (it's 36x48 instead of 18x24).
Offtopic: clicking the first link confused me, because that stretch of highway is so close to my house
