ولا في طعام قرية بعينها ولا ثمرة نخلة بعينها
Translation: Nor in produce restricted to one specified village or fruit of one particular palm.
The muslam fih is a described obligation owed by the seller, not a contingent crop from one source that may fail entirely. Restricting it to a particular village's crop or one specific date palm defeats that general deliverable obligation.
An obligation to deliver 200 kg of defined dates is different from promising only the future dates of one named palm. If that palm bears no fruit, the second arrangement leaves the very subject of the bargain exposed to failure.