Well, the counterargument - which we've all heard, and probably used ourselves - is that in cases where there is such "correct MI", the NOS didn't get the same information partner had about the bidding - the fact that they switched recently, and it used to mean [this]. This causes two problems: first, partner could later in the hand figure out that partner misbid, and therefore almost certainly what they have (the first only is possible for the NOS), and second, the NOS may misplay in a way that they would be less likely to with the correct information (especially if they get an inkling that there has to be a misbid; again, partner and only partner can work out what the likely misbid is going to be).
Something has to be done, and it's probably best to have a regulation that handles it, so that the players don't get "but it happened this way when I did it a month ago with the other TD" (or at least if we do, that there are words to pin the argument back on).
As I said above, I don't think the regulation as reported is the right way to go, as it's highly inflexible and doesn't compare "auctions that happen all the time" with "auctions that may only have come up once, or in practise" as far as "how much experience one needs to have with a system for it to be a legitimate forget". After all, at least around here, the people who "forget" their weak NT defence against us are almost always long-term established partnerships, who have been playing this for well over a year. They get protection for their "forget", but I'm stuck with MI ruling for mine because we switched 6 months ago, even though it's an auction that comes up once a night?
The above is actually my last forget: The auction went
1: No Alert, asked and explained as natural, very uncomfortable bidder
2: Alerted, range ask. I hope it wasn't obvious that there was a very uncomfortable bidder
3: Minimum, I assume :-)
*They* play DONT over strong NT, and natural over weak, and have for 4-5 years. Overcaller forgot, because they never play against weak NT. *We* play systems on over 2
♣ interference (whatever it means), and lebensohl against higher. *I* forgot, because I play systems on over X and artificial 2
♣ only with all the pairs I play a strong NT and Stayman with. But the 1NT(weak)-2
♣(whatever it means) auction has come up much more for us than for them, even though we switched to Keri 6 months ago. According to the Dutch regulation, they're in the clear, but we (who used to play this as "systems on = natural, to play" before) misinformed.
When I go to sea, don't fear for me, Fear For The Storm -- Birdie and the Swansong (tSCoSI)