... I have been told different by J. Lloyd park rangers?
Pat-tekker, I can't comment specifically, but here's a general comment: So too in CA (to use an example) have various md'rs *occasionally* been confronted by park rangers on our state beaches, saying various supposed rules. Eg.: "You can't do that". And a few of those md'rs shook in their boots, taking the warnings to heart thinking "this is the rules for CA" (hey, can't argue with a "duly-appointed state ranger",
now can you?) And on a few of those occasions, others of us who got wind of this flap, went to try to "clarify" it (since it's general knowledge you can detect state-of-CA beaches till you're blue in the face).
Bottom line is, there is nothing *specific*, yet there are various catch-all grey area wordings which could apply. Ie.: cultural heritage, lost & found laws, harvest-&-collect laws, etc.... And the end result of those various altercations (perhaps not un-like your own), is that they are forgotten and ignored. You can still detect to your heart's content, and no one ever sought clarification, or whatever.
Perhaps this is what's happened to you: You just ran into a singular ranger having a bad day ? An over-zealous archie-minded type who's since-been re-assigned elsewhere, so you can just disregard now ?