I've bought some of the blister bandages before and thought the main point was how they apparently cushion: not so! In fact, they should only be used on "deroofed blisters" and not on nascent blisters. This time i did some reading, and found another technical term: exudate. Apparently, the hydro-colloidal bandage absorbs the exudate to create the healing environment that makes them so effective.
This post by a podiatrist explains quite nicely, using "weeping" for exudate.
Anyhow, i hope i'm treating this very weepy deroofed blister correctly now.