Cougar Mountain is an easy drive up near Seaside, OR. Or is it?

The conundrum comes because of two gates. Both were open when I went up, neither had signs, not even the seemingly mandatory warning about closing at any time. I rolled the dice this time, but now that I know what's up there I'll bring a bike if I come back.

Here are the directions which work regardless of your mode of transport. That includes the carefully driven passenger car, although this route had less than the normal amount of potholes, so not so carefully? Watch out for log trucks anyway.