My experience is that band tighen more firmly and never move. Until the band snaps. Alwaye use a piece of high quality transparent tape under the band as the adjustment process can make a mess of your paint.
Bands were also useful when you used non standard or modified tubing. I had a late 80's Douglas mtn bike with oversized, ovalized tubes near the BB and that same Deore DX shown in your pics was the only FD I could find to fit, The band shapes itself to the tubing profile.