if you don't think it's a psychic, then you think it's a reasonable deviation from your system. If your partner also thinks so, then it's part of your actual, if implied agreement. If it is your agreement, then it has to be legal in the game you're playing. From what I can read of the NZB systems regulations, that's not an issue, but don't trust me for that. And the opponents have to be as aware as you are about it.
It's much better for you that a "deliberate, gross" deviation from your methods be considered a psychic. And a "four card suit" on 654 and a doubleton - yeah, to me that's gross. You've already volunteered deliberate.
You're not the first to want to bid a 3-card major on the odd hand that is unsuitable for anything else in your system. My experience with pairs who do this (not exclusively, but pretty much) is that:
- "It's normal, everybody would do it, why do we have to tell the opponents?", or
- "It's very rare, and everybody has some hands that system doesn't have a bid for, why do we have to say anything?" (or better yet, "it's just bridge"); and
- "But of course it's not psychic, I don't psych!"
Now, I am 100% biased; in the ACBL, an agreement to respond in a 3-card major was not legal in 95% of events until 2017 (and still isn't, on the Basic charts). And we have the "Thanks for the Bulletin's clever" attitude to psychic bidding by most players. So the people who would do this (or designed their system to require this) were in a bind, where what they wanted to play wasn't legal, but they couldn't claim it was a psychic (even if it was), because then they'd be tarred and feathered. More enlightened places in the world might see different patterns.
If I did this (and partner wouldn't expect it!), partner's response would be 4
♣ splinter. But that never seems to happen to anyone else.
As far as the opponents are concerned, if they can't resolve a psychic 1M response either immediately or later, maybe they should look into fixing that, or paying off to it when it happens, depending on the relative EV.
When I go to sea, don't fear for me, Fear For The Storm -- Birdie and the Swansong (tSCoSI)