MCAS apparently only operates with AP disengaged. The fact that the EAD refers to the runaway trim procedure seems to indicate that the FDR indicated runaway trim. As I've mentioned elsewhere, if MCAS is implicated it means the pilots were flying by hand and counteracting MCAS auto-trim activity reasonably successfully up to a point. What happened to change that situation and trigger the horrific descent is very much unknown.
Earlier in this thread or somewhere else, possibly in an AAL union pilots blog, there was either a Boeing or an AAL quote that intimated that if the cutout switches did not stop the "runaway" trim then you should hold the wheel as in the procedure. There was some skepticism about the success of doing that in the AAL blog. Someone else in this thread pointed out that the trim could still run away due to welded contacts and CB pulling would be required but I don't think that is relevant. I hope that Boeing did not engineer a MCAS circuit that bypassed the cutout switches but the "hold the trim wheel" verbiage makes me, and a few other posters, wonder. So if the crew fought the MCAS with trim and finally used the cutouts, would the MCAS still work and now they had to crank the trim wheel. But that doesn't explain why they let the birds airspeed get so fast.