Does the omission of mentioning wiping the ears in the ablution in Bukhari and Muslim, despite its mention in other hadiths, constitute proof of their lack of authenticity or the Prophet's infrequent performance of it?

The fact that Al-Bukhari and Muslim did not include a hadith (definition) does not mean it is weak, as they did not commit to encompassing all authentic hadiths, but rather aimed to collect a selection of them. They might authenticate hadiths not found in their books, and they might weaken a hadith that others authenticate. Therefore, the absence of mentioning wiping the ears in the two Sahih (definition) collections does not mean it is not legislated. It has been authentically reported by Al-Tirmidhi, Al-Nasa'i, and others, and many scholars, such as Ibn Abd al-Barr and Ibn Hubayra, have reached a consensus on it, except that Imam Ahmad considered wiping them obligatory.