Yes, they're doing something different. They're putting something on it that retards its growth. That's why it keeps so long. Most vegetables are sprayed or soaked with a growth retardant.

They may be dipping it in a food-safe wax type anti-transpirant/anti-dessicant to dramatically slow down water loss from the surface.

Mine will keep from 4-6 weeks in the fridge in the green bags. Ironic, but they keep better when on the dry side in the bags, because moisture promotes the growth of mold even in the bags. I've found it helps to take them out of the bag about once a week, wipe them down with a clean, dry paper towel, wipe out any excess condensation from the bag, and repackage.

I cut mine into convenient lengths to bag - the cut surfaces form brown, corky "suberin" tissue, which is cut off and discarded before use.

Finally, consider using the excess for something like a freezer daikon coleslaw or a refrigerator pickle -- I made up a bunch of the freezer slaw this fall with my excess, and its a great addition to meals or even good on a hotdog or sausage on a bun with onion and mustard.

I have grown Daikon and other fall storage radishes for years, and they keep for months in the vegetable drawer of the fridge. No special treatment for any of them. In fact, I used one the other day; it was picked in early November. I do suggest putting them in a plastic bag and keeping it lightly closed up.

You might also consider pulling them earlier (smaller) and plant in succession so they aren't all harvest size at the same time. This is my solution for zucchini!

Just me thinking since I don't grow them, so take it for what it's worth. :-)

Deanna