Why have different materials been used in the crawl space?

[Hispaniola]

My first question here on the forum...
Today I cleaned the crawl space and under the plastic (therefore no plastic in the picture) after the carpenters' work in the cabin last winter. I wonder why they used different sheet materials, OSB and the other board, which is also not consistently used with the same side down. There has already been exposure to the known humid environment on the OSB boards...in my understanding, I was convinced they would use tongue-and-groove boards that I would linseed oil impregnate. I asked if we should specify more in the job agreement, but they said it was not needed. I would have liked to have wool insulation and was prepared to spend extra money on it, but they recommended using the loose-fill insulation which I then approved. My work with the crawl space is not finished, but it feels more and more difficult to proceed with all the mixed materials, trying to clear out all the mishmash that might start to smell and mold, thank you