ثُمَّ يُضْجَعُ عَلَى شِقِّهِ الْأَيْمَنِ، فَيُغْسَلُ بِالْمَاءِ حَتَّى يُرَى أَنَّ الْمَاءَ قَدْ وَصَلَ إِلَى مَا يَلِي التَّخْتَ مِنْهُ
Translation: Then lay the body on the right side and wash with water so that the portions previously touching the platform are also reached.
Turning to the right exposes the left side and other areas that could have remained against the platform. Both side-washes serve the same objective: reaching every part of the body.