Hi Luca,
Many thanks for the reply and thank you for taking the time to reply and include an illustration and link to the document "An Analysis of Bowlines". It makes me a little ashamed that, in my haste to post in the middle of a working day, I did not have the time to include an illustration! The document looks fantastic, and I look forward to reading it in its entirety.
I have attached four images. The first two show the knot which you have described. The second two show the know I attempted to describe. The difference is that your version includes a 360 degree turn around the "eye-leg of the tail side" before the figure of 9 (and appears to remain a bowline), whereas mine does not. Although it is not obvious in the untightened picture, when tightened this appears to remove the nipping turn or, at least, completely destabilises the knot. That said, it seems reasonably secure under load, although have not tested this... However, the lack of a clear nipping turn means that it is probably no longer a legitimate member of the bowline family.