This is not requerment. First generation of WP7 phones had few curvy models, but square corners was a trend already. Flashy colours were popularised by Nokia, they had similar design before switching to Windows Phone, so HTC and Huawey just copied them for WP models. Samsung Ativ S is example of curvy black WP8 phone.
More like Elop came in, killed the entire MeeGo pipeline (except for the one phone they were contractually obligated to launch), and then used the MeeGo hardware to launch his WP7 stuff sooner.
