Hello Ronan,
thank you for getting back to me. I understand what you are saying, this is not the same as a hook modifier, an additional bone would be needed to get the desired falloff to work. I know envelope weights should not be compared directly with automatic weights, but additional bones or vertex groups are not required to get auto weights to falloff smoothly. Putting that aside, if we add another bone to get the overlapping influences between bones, then we still do not get a smooth falloff. I have tested with many simple scenes and found no result has a smooth transition, so I believe there is still a bug here.

Nice workaround Seth.
Smart thinking!

Can somebody else step up to have a look at Bsurfaces bugs?

mont29 assigned this to eclectiel, but I was told he is no longer active.

The attached file was accidentally put at the start of the description, before 'System Information'.
You may want to move that to the bottom of the description text.