See the video in #148412 for an example of flipping back and forth between the 2-pass Gaussian blur and the RRect fast path:

There's quite an extreme difference between the two blur paths. In this example, the apparent standard deviation of one appears to be more than twice the other. This will continue causing issues for users because the RRect fast path is an opportunistic optimization and not a discrete path exposed to Flutter.

There is one correct solution for rendering a Gaussian blur with any given shape and sigma. It's perfectly okay if we slightly deviate from Skia in our blur's appearance, but our multiple blur paths should at least look remotely similar.