Double Tap Gesture (Watch Series 9) Doesn’t Work with Family Setup

My daughter saved up her own money and asked for Apple gift cards for her birthday to buy herself an Apple Watch. She was very excited about the double tap feature (initially, it didn’t work because WatchOS 10.1 had not come out yet). She knew double tap was going to be in 10.1 and checked every day to see if the update was out. After we installed 10.1, the double tap feature still did not work. Why? I don’t know, but I found this article [If double tap isn’t working on your Apple Watch](https://support.apple.com/en-us/HT213942) which states:

> Make sure that your watch isn’t paired as a [Family Setup watch](https://support.apple.com/kb/HT211768).

... without further explanation as to why these are incompatible.

Why would Apple disable the flagship feature of the Series 9 for seemingly no reason?! Double tap and Family Setup have nothing to do with one another. This is infuriating and disappointing. I feel ripped off. We paid more to go for the Series 9, mostly for this feature.

Is Apple planning on fixing this in a future software release? Or should I go get my $ back and buy a Series 8?