Help
OP said:
3♦ was intended as a good heart raise on ♠J10x, ♥ Q10x, ♦Kxx ♣AJ97 not alerted, they'd agreed bidding opener's suit was a raise
East did not "improvise" a raise, they thought this was a raise (at least from the OP's perspective. Usually we assume the information in OP as read/determined. Here, of course, with it being the opponents, the director should ask and find that out, and not assume. But I've seen it before, and would believe it.)
Absolutely, if East decided to bid 3♦ because it was a "general force" (which is no less sensible than "cuebid"ing as a raise), then the chance that passing rather than showing the hearts is less likely. We'll see the poll.
But as far as UI is concerned, it doesn't matter what their agreement is (for a potential MI ruling, of course, it does). If East expected an Alert, and didn't get one, even if that woke her up to their agreement (general force, natural, whatever), that is still UI to her, and the UI still is "partner doesn't know I have hearts" (in this case, "because I didn't show them" rather than "because partner's forgot the system", but still).
Re: Gilithin, yes, that's the argument. However, the "let's say" numbers are the/a problem. The relevant leg of the UI ruling:
Quote
...[T]hat is demonstrably suggested over another by unauthorized information if the other call or play is a logical alternative.
"Demonstrably suggested" is the issue here. All Gilithin's numbers should be doing are demonstrating that 4♥ is suggested by the UI over pass. And I agree, if 3♦ "was intended as" a heart raise, and it wasn't Alerted (and should have been), there was UI and that UI makes "make clear you have support, partner doesn't think there's a choice of games" suggested over passing a "choice of games" 3NT. But by using the numbers he is using, he is begging the question of Logical Alternative. Clearly, "40% would pass" meets the "significant proportion...would consider, and some might select"(L16B1b) Equally "demonstrably", we could use "10% pass/90% bid" and "3% pass/97% bid" - but now it's much less likely that by throwing numbers out like that, we meet the "significant proportion" criterion.
I am not assuming that is his intent, but it is something to be careful about, because it happens A Lot.
I've been carefully avoiding "do I think that pass is a LA with this specific hand?" in this discussion. First, that's up to the poll; second, the discussion of how we would rule is more interesting than is "is passing a LA with 23-27 HCP and a 3334 with effectively perfect spade help?" Especially because we don't have information about whether E-W agreement on "bidding over preempts" looks more like OP's (in which case you are definitely wondering about 23 to..." or mine (where you would have to rephrase the question "...with 26-28 HCP and..."). And that is an interesting question - my case looks like the traditional "extras and flat, likely to make the same tricks and get the extra 10 points at matchpoints", and OP's looks like "minimum values, wasted values in spades, it's possible we make the same number of tricks in NT and that number is 9". Without knowing what hands will not be preempted in this partnership, we can't even work out what would be a good pass.