'1' threshold value would only allow to access a third of the basic
'color space' (from black to white, from 0.0 to 1.0 component values),
when you expect it to access the whole range.
Unfortunately, this needs a subversion bump to allow already defined
brushes to keep exact same behavior!
Also, did not change default value (0.2) for new brushes, think here
keeping current one makes more sense.
Thanks to @LucaRood for confirming the issue.
f6083b7bcd