Kind of a strange explanation, but not completely bogus. Maybe he's afraid to give a clear explanation 'cause you'll do the job yourself. I can guess a couple different things he might have meant...

Honda rear calipers have the auto-adjusting ratchet for the handbrake. You have to twist the pistons, you can't just push them back in. Every so often you see a thread here about someone using a C-clamp & destroying his rear calipers.

Front or rear, when you push/twist the pistons in (to make room for new pads), you push fluid back to the reservoir. Watch that the reservoir doesn't overflow & make a mess. Some mechanics like to suck some fluid out of the reservoir, some like to open the caliper bleed screw. Sometimes it's just a good excuse to bleed the entire brake system with fresh fluid.