Apparently that the park was recently closed?
Or the author just claims it was.
Yellowstone closes various roads and entrances every March for grading and upkeep. Everything opens back up the first week of April. I think the main paved highway stays open year round but most of the visitor buildings will be locked so don’t count on any bathrooms being open.
I thought they seasonally closed down certain areas of the park as a matter of course? Winter danger and all that...