b-s-i was actually pulling the latest snapcraft, but it had to be downgraded as explained in Builds failing automated review. The review-tools version that works well with snapcraft 2.43 was deployed to the snap store on Tuesday, so I imagine as soon as @jdstrand gets a moment the downgrade can be reverted.
To be clear, pulling the latest snapcraft was and should be the normal behavior for b-s-i, and I believe b-s-i builders install a very up-to-date set of tools every time before starting each build (save for the exceptional snapcraft downgrade I mentioned).