There has always been basic indications that the Rolemaster spell realms operate under different mechanics. Essence and Channeling are affected by armor, Mentalism by helms, verbal and hand gestures are necessary components of Essence but not so much Mentalism etc. At the same time, the general casting mechanics of 3 rounds for most spells were uniform across the three realms without any serious mechanical differences.
Most of these rules were more the result of built in game tropes, the need for “balance” and to facilitate gameplay (combat) than any rigorous attempt at realm differentiation. During our Spell Law rewrite (Project BASiL), we started from scratch—deconstructing the various spells, powers, categories and casting requirements and then rebuilding spells and realms in an intuitive and organic fashion.