This cl: https://chromium-review.googlesource.com/c/chromium/tools/build/+/1056347 was necessary because the assumption that all builders would have a commit position as a property of their bot update step was wrong.

There are builders downstream that do not have commit position for their root solution revisions (e.g. android)

Depending on how flake analysis deals with this, the isolate build index should provide a workable solution.