mycroft, on 2025-February-11, 10:39, said:
Wait, who? Why? :-)
Probably better to restrict ourselves to why, although that is the only answer I don't know :-)
I wasn't a TD then, but to the best of my knowledge our regulations at the time didn't set any specific limits on shapes "allowed", or even say "balanced": just a general principle that to open 1NT shows desire to play in NT (which I always found uncomfortable because even holding a 4432 I desire to play in a major, not NT, if partner has fit and most strengths). But I think it was tacitly acknowledged that one could agree to open 1NT on a 5 card major and maybe even a 6 card minor, but no more. Going from that to illegal agreement is quite a stretch, I agree.
Shortly afterwards the regulations for pairs tournaments were changed to allow a precise set of shapes, including 6m322 and any 5431 but not 7m222.