This is just silly, I've worked on systems to write text and that is just wat you do to solve the problem of (collaborative) editing a document.
It's probably one of those situations where you'd write a "Diversion Report" for the security team where you talk about limited assets at rist and a huge investment in engineering resources.
Storing the change vector is essential for collaborative editing in the moment. But the UI should highlight a Flatten feature as part of explicit Saving or Sharing actions.
FYI - this is a kind of 'biometric' leakage eh.
Your typing style is probably as unique as your finger print.
It's not shockingly bad, but probably something, under thoughtful review, they should take care of.
Edit: by 'no use case' I mean, no use case for long term history. Obviously there's a good use case for 'very short term' individual keystrokes.
Also Edit: the answer to this issue is not 'Don't worry about it, it's a low risk problem'. This is the 'slow boil' SV way of thinking that is seemingly benign, but not acceptable in the long run. The answer is: don't store personal data that is unnecessary. It's that simple. It doesn't diminish the product a single bit.