Allow me to repaint this paragraph of the EU-OPS a bit.
(b) When complying with sub-paragraph (a) above, an operator shall ensure that the minimum number of cabin crew is the greater of:
(1) One cabin crew member for every 50, or fraction of 50, passenger seats installedon the same deck of the aeroplane;
So by labelling installed seats crew rest seats and not accepting passengers to be seated or booked on them, the law seems to be fulfilled as well.