The
Q&A can give you a definite answer, if you can get thru, but it sounds to me like they mean:
You can decide to have the compressor onboard or offboard. The onboard compressor weight is not like the battery or ramps, it DOES count as part of the weight of the robot. Leaving it offboard saves weight, as the compressor won't be part of the robot's weight.
The note means that your offboard compressor plumbing and wiring systems need to comply with the robot rules, as far as how it is connected, having pressure regulation and safety valves, and other safety considerations.