Found due to builds kicked off by #74447

https://dev.azure.com/dnceng/internal/_build/results?buildId=2504035&view=logs&j=7ae71e7c-d4fe-51ea-64cd-240849b77ab1&t=e2756d63-0606-58d5-0f0d-91c79a5ba922

It looks like RIT is not handling the case where default.config is present, which is only in these old branches, not in the more recent ones.