الجواب وبالله التوفيق

At the time of wudhu it is a fardh to wash the hands and feet one time, washing it three times is a sunnah. You have an incorrect understanding, it is a sunnah and not a mustahab(liked) and mustahab is not equivalent of wajib(mandatory). However leaving a sunnah without a reason will lead to a person becoming sinful.

Therefore it is better to follow the sunnah of Rasulullah Sallallaho Alyhi Wasallam and wash the hands and feet three times each. This will make up for any shortcomings of the fara’idh.

واللہ اعلم بالصواب