Earlier quoted context omitted.
The "default" keyboard differs from device to device. Most devices have a closed source keyboard either from Google (gboard) or from Microsoft (swiftkey). If I remember correctly, both send subsets of what you type to the mothership and pinky swear to only use it for product improvement and guard your data with their lives.
So Xiaomi, Google, Samsung etc. knows everything we write and erase? I getting really paranoid...
No idea about others.