A Lexeme with only an arabic lemma, when shown on Special:AllPages, shows the lemma marked-up as lang "en" and dir "ltr".
Apparently T195382 did not make it to production in full, yet. Production is still at (593cade). Visually however this does not make a difference, the mark-up is slightly different from what the "final" version will be. /cc @Lea_Lacroix_WMDE