Magnetisim is not a test of whether something is made from stainless or not.
There are probably 20 or so common alloys of stainless, with another
20-50 uncommon ones. Of these, a couple are pretty much nonmagnetic- 316 is pretty reliably non magnetic. Many others, while still considered "stainless steel" are magnetic to varying degrees. Most common stainless is 304. This is relatively nonmagnetic as rolled, but if cold worked much, gets more magnetic. Also, if forged, it can get more magnetic. So if it is rolled to a thinner gage, then bent or punched or rolled, chances are it will be magnetic, although less so than mild steel is.
I cook a lot of oysters on my grill, so I have replaced the burners, heat diffuser, lava rock tray, and grates with all stainless material. I also have a scratch built charcoal barbecue that is all stainless, for those big oyster cookouts when you need two barbecues at once.
I dont bother to keep em shiny, though- they are stainless so they dont rust out, not for looks.
Personally, I think Ducanes are overpriced for what they are- the Aussies make really kick butt barbies- I have had the same barbie from Barbecues Galore for close to 15 years now, and had another one for 8 or 10 before that that I had to leave when I sold a house- very well designed, sturdy stuff.