وَوَجَبَ عَلَى الْمُشْتَرِي قَطْعُهَا فِي الْحَالِ
Translation: And the buyer is obliged to cut and remove it immediately.
Al-mushtari means the buyer, and qatʿuha means separating the fruit from the tree.
The buyer acquired the fruit, not the seller's tree or land. Ownership of the fruit by itself does not give the buyer an indefinite right to keep occupying the seller's tree.
Classical Hanafi explanation connects immediate cutting with freeing the seller's property.