That is a very good illustration; but it shows two ropes joined at the end.
The Bowline I tie is the left handed variant, also known as the Horse Knot; presumably tied this way to keep the tag end from rubbing against the horses neck. However, I also know that several countries naval service teaches this variant as it is considered, by them, to be superior. I can't speak to the superiority but it is easier to tie up the sailors way, for me, with the tag on the outside; and if Denmark thinks it's good enough then I will use it this way. It's not wrong, just a variant and a recognized variant at that (ABOK # 1034 1/2). I have neither see nor heard it reported that a Left Handed Bowline capsized or inverted as I show the Sheetbend doing. If you have a source for this I would very much like to read it.
My point is this: If you tie up a loop in the end of a rope using a bight and the Sheetbend Join you create a slip loop that could cause very serious damage. The Bowline will not create a slip loop in this manner.
I guess, if you tie a Bowline and then cut the loop you have a Sheetbend Join; but you can not tie a sheetbend to form a loop at the end of a rope with out the loop being able to slip closed.
The Bowline will not form a slip loop; that is why it is the preferred rescue knot. It may spill if not backed up and the loop will come apart, but it will not cinch closed.
The Bowline has a standing end and a bitter end
The Sheetbend has two standing ends and two bitter ends
The Bowline has three load bearing ends
The Sheetbend has two load bearing ends
Cutting the loop of a Bowline to create a Sheetbend does not mean they are the same; if that were true then a Reef Knot would be the same as a Cow Hitch as the Cow Hitch is just half of a capsized Reef Knot!
They are not the same knot.
This is what got me started on this years ago and why I teach it now; telling people that the Sheetbend and Bowline are the same may cause serious harm. When someone believes this, and they use the Sheetbend to form a loop instead of the Bowline, and end up getting hurt, it will not be because I gave them bad information.
Believe what you like, but for your sake, please don't use, or teach, people to tie a loop in the end of a rope with a Sheetbend; it's the worst kind of dangerous, the unexpected kind.