Collision was the top risk according to the Duty Holder, Major General Felton, but still he signed off to say the risk was tolerable and ALARP.
Because with a program in place to fit a Traffic Awareness System to the Puma there was nothing more that could practicably be done. There was presumably no way to speed up the installation of the equipment without incurring excessive cost and/or grounding the Puma fleet. If you incur excessive cost by speeding up one programme you'll invariably have to cut back another one, e.g. Chinook TAS, and if you ground the fleet waiting for mods to be fitted you'd never have anything flying.