Well I rather hoped that some educated ATC er would point me in the direction of the evidence used to establish these rules with helicopters rather than just pointing out what MATS says.
If it is a problem at the airport you’re based at maybe try to approach the airport authority and ATC unit. They they may be able to improve their procedures for example providing dedicated areas for helicopters to operate in which are deemed separated for wake turbulence purposes (see
Wake turbulence seperation from helipad (less than 760m) to runway) and cross helicopters where they won’t be crossing the flight path of the fixed wing.