Is the name "Saleh" disliked for naming due to the possibility of it being a commendation of its bearer, or due to the forbidden practice of tatayyur (superstitious pessimism/optimism) as in the hadiths that prohibit naming with "Yasar," "Rabah," "Najih," and "Aflah"?

The prohibition mentioned in the hadith against naming oneself with names like "Salih" and "Ya'la" is not for prohibition (tahrim) but for disfavor (tanzih), and the reason for this is due to the repulsiveness of the answer or fear of ill omen. If the reason ceases to exist, and the naming is not intended as a purification or there is no fear of ill omen from it, then there is no objection to using such names. The Prophet, peace and blessings be upon him, remained silent regarding the prohibition of these names, as did Umar, may Allah be pleased with him. This silence was a mercy to the Ummah, and the mentioned prohibition is to be understood as disfavor (tanzih) and not prohibition (tahrim).