Yep. If you're messaging on Signal, but you're typing your messages on Gboard, your messaging is not really guaranteed to be private. 
nostr:nevent1qqsf4ctux40qt3rayxyg4elxx7fvjky73yzuwfwx5rmzqxxj3848ckcpz3mhxue69uhhyetvv9ujuerpd46hxtnfdupzqgd5rygzm28upw5sfp9wey6t74dh408htmkm8yfyart4ujglgxj7qvzqqqqqqy3gvzhh