I've opened a file where the text is fairly narrow -- longest line is 91 characters.
When I toggle softwrap the line spacing changes.
With softwrap off, the editor window shows lines 1 to 62.
With softwrap on, this condenses to 1 to 66.
To be clear: No lines are actually wrapped. The window is much wider than the text.
Font is Courier new, size 10.
This happens until I set the font size to be 18 or larger.
HM... seems to change.
Now when I set my font back to size 10, I get 1..63(wrap off) and 1..68(wrap on).
Looks like the line spacing at font size N and wrapoff is the same as N+1 with wrap on.
This doesn't happen with a clean configuration.