For what it is worth, the old Frei0r based Gaussian Blur filter had the same behavior.
The new Gaussian blur filter is not a pixel accurate replacement for the old one. The algorithm is considerably more efficient and the range works differently. So people will have to experiment with the parameter to achieve similar effects that they are used to from the old filter.
I like your thought process on this suggestion. My concern is that this would dedicate the Shift+Alt modifiers to only work for track moving. We wouldn’t be able to use that combination for any other keyboard shortcuts (e.g. Shift+Alt+T) because every time you hit Shift+Alt it would trigger the track movement operation.
Also, it is very late is the process to make a major change like this. It would probably delay the release by a month. And I would like to move on from the track movement feature to other features.