so, in a systems outage situation, ATCOs attending to what were once ATSA tasks in addition to their own tasks is no less safe?
Having worked in an EFPS-equipped tower, I agree that the new technology can take the ATSA requirement away - I've seen it firsthand. However I've also seen one particular EFPS-equipped ATCO position go into one-armed paperhanger mode - even when the system is working OK - just down to sheer workload.
If the system went tilt (and there's never a guarantee that it won't) then for those left in the tower, the policy to remove the support staff may just get called into question.