why is there no seclusion and dress code for slave women in islam?

I know that Islam treats women with honor and that they are privilaged to be modest and such. However I do not see this reflected onto slave women who were instead obliged to only cover from navel to the knee. here is a hadith that I find troubling: أَنَسِ بْنِ مَالِكٍ قَالَ: " كُنَّ إِمَاءُ عُمَرَ رَضِيَ اللهُ عَنْهُ يَخْدِمْنَنَا كَاشِفَاتٍ عَنْ شُعُورِهِنَّ تَضْرِبُ ثُدِيُّهُنَّ “Umar’s maids, may God be pleased with him, used to serve us, revealing their hair and stroking their breasts.” Imam al-Beyhaqi records in ‘Al-Sunnan al-Kubra’ Volume 2 page 227 Why are the slave girls made to be immodest among these men. Is this not dishonorable to them and a source of fitna?