Newsflash: We bid on a listing and seller is asking us to legally subdivide the land we are buying from them.

Ok so we placed a bid on a house that is listed on 17 acres of land in Pennsylvania. The original listing was on 91.5 acres of land for $450K, it was taken down and switched to 17 acres of land for 194,900. We went to see the house this weekend and really liked it. We placed a bid for 191,000 as it is old, needs some work and has been on the market for over 200 days. Our realtor submitted the offer, the listing agent got back to her that the seller accepted the offer but is stating that we have to legally subdivide the 17 acres we would purchase out of the 91.5 total. Why was this property even listed for sale if it is not legally subdivided to be sold as such? Is this legal, and why would it be our responsibility? Is this going to be a huge dissappointment, we thought we had found our forever farm and are really bummed over this situation. Also the purchaser of this property bought it for 135,000 in 2016.