If I recall correctly, 10" is the required vacuum to achieve during extraction for non-licensed equipment used for a non-licensed application. If a license is required for the work (for example, you're getting paid), you must use certified equipment, and that equipment will draw 20".

Also, I recall that the fine is more like 25K per day. 10K goes to the snitch. That's quite an incentive to turn in your shop if you see them doing improper work, but I don't think it's really aimed at consumers.