These are both excellent questions, anonymous. With the first, it simply orients the inkay into the best position to become malamar, as their “caps” are more stable to serve as feet and support their weight. (Malamar lose their ability to float in the air for extended periods of time upon evolution, largely because they devote their telekinetic power to, well, battling instead.) That and their tentacles become unwieldy in inkay’s “right-side-up” position, but turning around allows them to develop into arms. Because of all this, if the inkay evolves without turning, the malamar will essentially develop into a giant inkay unsuited for land, so inkay in general are particularly careful to orient themselves in the best manner to ensure maximum mobility.
As for Mallomars, no, that’s definitely a coincidence. However, Pockychu is a different story.
[[Bill, Pockychu doesn’t even exist… —LH]]
The Pokédex According to Bill 