Did he open the bleeder screw on each caliper before he compressed the piston back into the caliper? That would just let the old fluid out of the system.

But if not, then that means he instead pushed a bunch of degraded fluid and debris back up the lines ... and potentially into the ABS plumbing. As you can imagine, this is generally not good.

If that's the case, you can and should try pressure bleeding, but this may end up being a very expensive brake job.

Good luck.