Opener bids a Precision 1D, partner responds 2NT, described in their system as showing precisely 11-12 HCP with no 4 card major.
Opener rebids 3NT.
Partner then bids 4NT and Opener raises to 6 NT.
When asked Opener says that his partner has obviously forgotten their system and has a bigger hand, so having a maximum opening hand he raised to 6.
Should this be allowed?