They have been doing these exercises for years. Ever since the end of the Iraq-Iran war the Iranian military has conducted annual large scale exercises.
It has been a traditional strategic option on the part of an aggressor to launch a surprise attack under the guise of "large scale maneuvers" near a border. This would be an opportune time for Iran to totally queer the deal as far as Iraqi elections, faltering US determination, and an immature Iraqi military, with an incursion in force across the border.