Is this HVAC condensing unit platform acceptable/stable enough?
That upper pad is probably not concrete, it's more likely Styrofoam covered with a coating to make it LOOK like concrete. That Styrofoam is actually better in some ways because it doesn't degrade or crack as easily as concrete and it absorbs vibration, making the unit quieter. Some jurisdicions however do not allow the styrofoam pads to be in direct contact with earth, hence the bricks.