For the record: I just got another piece of information from SAP Support:
When navigating from cell to cell, the screen reader will read out the contents of the cell. This is very important in order for WEBCUIF to comply with accessibility product standards
That's a very good point indeed!
So thank you for pointing this out: I'm glad you've finally came up with a relevant business case for those right & left arrows. However, when disabling the RowSelectionByLineClick which makes it possible to select content by double-clicking in a cell, navigation with left/right arrows is still possible so screen readers will work as well ;')
Cheers,
Nicolas.