cursor movement and combining character output

[mintty]

In 6.1, it says:

When the cursor moves to a grid cell that contains a complete or incomplete grapheme cluster, this grid cell’s contents will be erased and overwritten rather then textually concatinated. Therefore cursor movement semantics of the terminal remain unchanged.

The first sentence would contradict the second; placing the cursor somewhere does not erase anything. Only output of a non-combining character would implicitly erase the previous contents. Ouput of a combining character, on the other hand, should add it to a grapheme cluster even after cursor placement, not on the current cursor position however but rather on the previous one. Example: Text "abc", cursor is placed on b, text is still "abc", output of a combining accent, text changes to "ábc" while cursor remains on b.