This happens in suggested-edits, I didn't look at others
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When tokenizing the text for running the diff engine over the tokens, lengths of white space are condensed into a single token. So in your case, the token that had changed included the newline character. In code blocks this looks weird, because here a newline actually has a meaning (unlike in normal HTML text, where it's just like any other whitespace).
The next build fixes this, so only if a newline is actually added will this be visible, like this (hypothetical) edit: