Air Purifier is not an accessory and is a connected device, so I assume the app badge actually works (non-connected device badges currently don’t). I don’t know for sure, but I assume stickers for the next few rounds of products were printed before Wyze decided to discontinue preordering. Was your Air Purifier sticker a backed sticker?
There are items still shipping with backed stickers. Some are backed stickers, some are regular stickers. Some backed stickers are still being received for products that never went through preorder. I just received another set of Climate Sensors and Night Lights with backed stickers in the boxes. I didn’t preorder either product and they launched a while ago. Either Wyze doesn’t know what stickers are in which boxes or they have lots of extra stickers. 
The entire app badges and stickers process is in disarray. 