Hmmm....I can't see any reason for sending in your forks to have the sub-tanks mounted. In fact, I think they may have to be mounted behind your number plate, possibly on the triple clamps. It may be that they want to give your fluid the proper height for the tanks to be effective. Maybe they are going to re-port your bleed hole for a differnt size fitting, being the stock fitting is the biggest (or smallest, as it were) restriction that would hinder the flow controls from perfoming properly.
OR...maybe Ross wants you to feel it would be good to have a revalve at the same time. :D I have a feeling that when you get your forks back you will have instructions on how to then mount the tanks.
Although I feel that Ross has come upon a major item here, it's not rocket science. It simply allows you to change the volume of space on top of the oil.
I think many will agree that Enzo is quite a reputable company and you will probably find they do great work.