According to the build stages documentation:
[E]ach one of the stages runs one after another, and will only proceed if all jobs in the previous stage have passed successfully. If one job fails in one stage, all other jobs on the same stage will still complete, but all jobs in subsequent stages will be canceled, and the build fails.
However, in a recent build of sass/dart-sass, this didn’t happen. In the Deploy 1 stage, the npm job failed and the pub job was canceled, but the Deploy 2 stage ran anyway.