There are a few differences,
JS, between setting the parking brake and an RTO Autobrake application.
On the 737, the parking brake applies less than 1000psi at the wheels - this figure is not to be confused with hydraulic accumulator pressure. For an RTO, full braking pressure is applied at 3000psi with no modulation for deceleration scheduling - it is the maximum possible. In an RTO event, up to five times the energy is absorbed by the brakes compared to a normal idle-reverse landing.
As Mr. B. indicates above, anti-skid is active for RTO braking but not with the parking brake applied.