The missives state that specifications can be changed to products of an equivalent standard. We suspect that these M2 fittings are a lower cheaper standard than Crabtree, for a start it's pretty concerning that every electrician that I've spoken to (and I know a fair few) have never heard of M2
The developers have cut corners on a number of other products (Exterior Doors, Interior Doors, Sanitaryware etc) all of which have been replaced with cheaper, inferior makes, so it is a natural reaction to assume that they have done something similar with the electrical fittings