I'm really not sure you understand how it worked.
There was an Advanced Paramedic on the scene very quickly and he provided initial feedback to NWAS, who then mobilised sufficient resources and got them to the holding area as quickly as possible.
His job was then to triage the multiple casualties and to identify the ones that most urgently needed treatment. Those were the first people evacuated to the station foyer, which was the holding area NWAS had set up where they received any initial treatment to enable them to be stabilised & transported to hospitals.
The people who died at the scene were those already dead when the paramedics arrived or anyone who was so seriously injured that their chances of survival, even with immediate and aggressive treatment, was deemed to be negligible. And that's not a decision that was taken lightly or without good reason.
They were working as soon as armed police secured the scene and while they were searching for other devices. I know for a fact that paramedics arriving at the scene were told that the scene wasn't secure and it was their personal choice whether to go in or not. They all went in regardless.
There's nothing in the Kerslake Report that attached any blame or criticism to GMP or NWAS but maybe he should have talked to you & you could have put him right.