Nevadastars - go with your gut on this one, and not the Michelin cheering forum team. I hear the same comments over and over from people in the park I go too in Texas that bought Michelin a few years back.
I have the exact same issue with a 5'ver I own with those same expensive tires. The 5'ver only gets pulled 100 miles a year since they were new. They are about 5 years old now. Before the cheering squad say you have to move more to release the agents I'll cut off the internet knowledge with real world knowledge that they are others that move all the time with the same brand having the same problem. In the storage area there are rigs that move the same 100 miles a year with absolutely no issues with cracking, but they are using other brands.
Tell the current owner to make sure he registers the tires first at the Michelin website. I think he may have a claim against them for manufacture defect. Make sure you replace them. Once the cracks get that high into the tread area, you're asking for a blow out.