My position is: Freezing the display is better than a disappearance of the cursor.
You are of course entitled to your opinion, but the Scintilla developers (and its other users) clearly subscribe to the other opinion since they went to the effort of making wrap work in background so it wouldn't freeze.
If I do the test in the editor Featherpad when 'Wrap Lines' is activated, then the cursor does not disappear.
Turning wrap lines on and off is a little different to pasting lots, but in fact it demonstrates the Scintilla behaviour very well, if you turn on wrap the same line remains at the top of the display, so if lines between the top of the display and the cursor wrap then the cursor is forced down.