I doubt your experience includes wrapping bars with bar-end shifters.

Bottom to top is the preferred method generally as it puts the non-overlapped edges of the tape in an orientation where they point to the outside of the bike so that hand movement towards the outside doesn't tend to raise the edge. But it doesn't work well if you have bar-ends and the housings need to exit from under the tape somewhere in the middle of the tape job. If you've ever done a wrap with bar-ends, you'd understand the problem: Bottom to top - unsightly gap in tape where housing exits; top to bottom - no gaps.

As to the technique where the tape "tightens" naturally as you rotate your hands back, that's strictly a question of CW or CCW wrap direction and has nothing to do with whether you go top to bottom or bottom to top.

Final comment: Technique and patience makes a lot more difference in the quality of the job than wrap direction or orientation. I've seen superb tape jobs done in the "wrong" way and they look great and work peachy.

- Mark