It is never made clear that an app is required either. Often devices have an app but you don't need it at all since it was just slapped on as a feature checkbox.
I recently got a pair of Bose QC 35 headphones and out of the box they are non functional until connected to the app. I had to borrow a phone to connect them to the app to set up and then thankfully they started working on my own devices with bt and wired without needing an app.
Headphones should just work out of the box. The only useful function the app provides is firmware updates and a way to map the button to NC level.
Bose QC35 headphones should be 100% functional over BLE without needing an app (I pair them with my iPhone as a normal BLE headset, and they pair with my Mac and Windows Desktop as well, no app installed).
Also, they include a physical audio cable which works all the time... I'm curious what could have caused your headset to not function normally, as I deal with many, many, many QC35s (my company gives one to each hired employee) and have never heard of (or experienced myself!) the app being a pre-req.
My mum got a pair and they just worked out of the box. Then a few months later I got a pair and when I turned them on they just kept saying to connect them to the app and refuse to pair to bluetooth. I then knew someone who got a pair after that and also had to connect them to the app.
Once paired to the app the first time it doesn't require it again and you can use them as regular bluetooth headphones. I'm guessing some product manager decided that not enough people were installing the app and had a change made so you were forced to use it at least once.
The physical cable probably did work. Initially I thought it wasn't working until I looked it up and found out you have to push it in harder before it clicks a second time
I recently got a pair of Bose QC 35 headphones and out of the box they are non functional until connected to the app. I had to borrow a phone to connect them to the app to set up and then thankfully they started working on my own devices with bt and wired without needing an app.
Headphones should just work out of the box. The only useful function the app provides is firmware updates and a way to map the button to NC level.