IsthisAbug. H3 beh. differently in IE / FF ?

Example:
Start the demo in *** IE *** at:
http://www.fckeditor.net/demo/default.html

Hit "New Page" button to empty the editor.

Then enter two lines of text and make sure there is no P tags inserted. New line should have BR tag (in this example).
Check out the tags in source mode before proceeding.... (Two lines with one BR tag in between.)

Then select the first line by left-click + drag.

Then select Heading3 from the Format list (dropdown) to insert a H3 tag around the first line.

In IE the H3 tag is applied to more than the text you selected.

If you do the same in FF or Netscape then the H3 tag is applied only to the text you selected.

Is this a bug in FCKeditor when using IE?
Or.....?