WinActivate causes tab change (Firefox)

[typhoon]

If I use WinActivate() with Firefox, it seems to change to the newest created tab automatically. Sometimes. Does the WinTitleMatchMode setting have something to do with it? Here is the relevant code fragment.

$title = "Mozilla Firefox"
   Opt("WinTitleMatchMode", 2)
   $x = 1287
   $y = 900

   WinActivate($title)
   For $i = 0 To 11
      MouseClick("left", $x, $y)
      Sleep(5000)
   Next