Has any credible musicologist explained that the double variations in Bach's Partita 1 for solo violin are a variation on the entire harmonic progression from the last movement and not just the bass line in a published work that I can cite?
In the age of Figured Bass, the "bass line" is the harmonic progression. That's what makes it infeasible to accompany most Bach pieces with strummed chords since you would end up with an inordinate number of chord changes and a lot of somewhat unusual chords.
It's somewhat easy to overlook this in Bach's work since the bass line tends to end up much more sellable as melodic material on its own than with many other composers.
So your realization is not exactly sensational.