According to your article, the closures are to motorized vehicles, which I understand it would allow foot traffic.
WMAs and large chunks of the National Grasslands are closed to motorized vehicles all year long with the exception of maintained county, state, and federal roads.
I am guessing that these closures in Oregon were primarily intended to keep out recreational vehicles (snowmobile and ATV/UTV). While we see deer herding up, often on private land, we don't see lengthy mass migrations of animals to specific areas. Well, the pronghorns will sometimes go south for the winter, but that's about it for us.