I find that if I buy a group of JFETs from an authorized distributor, Mouser for instance, it's extremely likely that all of the parts in that group will have come from the same die lot. Idss & Vp will be tightly clustered. On the other hand, if I buy a group of JFETs from someone further down the food chain, like Tayda, Small Bear, or Electronic Goldmine, it's likely that the parts will come from multiple die lots. Then Idss & Vp will be more spread out. OOP parts, like J201, are bound to come from multiple lots. The majority of J201s I've been getting from a reputable US supplier have specs that are tightly clustered, at least so far.