These discrepancies are due to differences between the morphological theories adopted by the UD treebanks developers and those employed by the developers of the morphological analyzers.
for Arabic, we adapted the morphological analyzer used in MADAMIRA (Pasha et al., 2014), which is built on top of the databases of SAMA (Maamouri et al., 2010) to output morphology that adheres to the UD Arabic treebank (Taji et al., 2017).