How did Sai Baba use Radhakrishnabai's service of sweeping to challenge the caste system's view on menial labor?

The provided text from Chapter 35 notes that Radhakrishnabai, a Brahmin 'worthy of worship by all,' took up the task of sweeping Baba's paths, a service that could be 'considered menial.' However, the passage focuses on her personal quality, stating that this 'dullness of thought never touched her faultless heart.' The text praises her clean and prompt work, highlighting her devotion. While this action is significant, the excerpts do not explicitly state that Sai Baba orchestrated this as a direct challenge to the caste system. Instead, it presents it as an example of Radhakrishnabai's own great humility and service, which followed the precedent set by Balaji Patil Nevasakar.