We used to plumb in fake fittings for SWG, in case the cell needed to be cleaned, the owner could still run their pump. Now I think its a non issue. Cleaning doesn't take the length of time that a pool store quotes lol.
As PRS said, if its plumbed after the cartridge/filter, I cant see anything being an issue. I can only assume SWG Manufacturers recommend this as a safety net in case someone inadvertently turns on the SWG before the 30 days.
My experience says that cells have issues with Ch.