I'm having a similar issue, too, with Siri being on despite taking steps to turn it completely and utterly off.
I have noise canceling headphones that I use on my iPad (for Duolingo lessons - it really helps you concentrate on the inflection and tone, i find). I use a wired connection, but if I turn on the headphones, without the wire hooked up, the Siri logo on my iPad comes on, as if it were trying to make a connection. It will disappear once I made the wired connection.
This happened, even though I had taken the following steps:
- Under Settings > Siri and Search: I had turned off "Listen for Siri", "Press Home for Siri", "Allow Siri when Locked"
- Under Settings: I went down to the listing of Apps, and under each individual one, I turned off "Allow App to access 'Siri & Search'". Doing that for each individual App took a long time!
Any suggestions of where else Siri might be unwittingly and unknowingly active on an iPad? I fear it is unescapable. Also, for what it is worth, I keep Bluetooth off. Always off.