I can't imagine why cypress mulch would be any different than cedar mulch as long as there are no chemicals added. But I sure wouldn't be mixing it into the potting mix, I'd leave it on top as a mulch to keep moisture in the soil and keep the soil cooler. Decaying wood chips in the mix will rob the soil of nitrogen.
Here's a cynical comment - don't forget that the growers don't care if that plant survives after you buy it. They'll pot their product in anything that's cheap and readily available, gambling that the plant will look good long enough to sell. That's the only reason I can think of why any grower would mix wood chips into potting mix for a container grown citrus tree. Or any other plant, for that matter.
Citrus here are grown commercially on heavy, rich muck soil, raised up on dykes for good drainage. Citrus have their feeder roots near the top of the soil, so a mulch is beneficial as long as it's not near the trunk.
If you want to grow bonsai trees that will stay small, maybe the lean mix with wood chip mulch mixed in would work, but if you're lookin to grow fruit, you gotta feed those puppies, and good soil is the start of good feeding.
