Random thoughts.
I'd ask how "summer" and "winter" apply here. If it's 9 holes for just 3 summer months, but 18 holes for the other 9 months, I'd think I'd consider it an 18-hole course, and put a prominent caveat about the summer closings. An enterprising local could update the local conditions as summer commences, as well. But most of the time, it's 18.
One caution about listing 2 layouts, or as 2 courses, is that a player may go there expecting to play both layouts. Not quite as bad as expecting to play 18 holes and only having 9 available, but the same principle.
We have a private course with overlapping layouts, and have spent 15 years trying to fit an evolving square peg into the round hole of this, and other, sites. One of the great pleasures of disc golf is its variety, but it's tough asking or expecting websites to accommodate every unusual situation.