I tested that issue on 2 smartphones with a lot of Xbox accounts/without Xbox live, with similar Google account. When starting the game, multiplayer automatically turns off, but I still can play on servers/connect to my friends/play Realms. My friends can't connect to my game. In world's options multiplayer is still turned on. On Windows 10 everything is ok. It doesn't happen when I play with Wi-Fi. I turned on "use cellular data” but nothing happens. 

That issue is happening with Minecraft on my smartphones from Minecraft 1.13 after getting Minecraft Earth skin* and it still happening.

*I'm not using that skin, I'm using Steve skin.