Is it obligatory for one who joins the prayer late (masbuq) to perform the two prostrations of forgetfulness (sujud al-sahw) due to his delay from the imam, even if the imam did not make a mistake?

The reason for the prostration of forgetfulness (sujūd as-sahw) is forgetfulness in prayer, whether due to an addition, a deficiency, or a doubt. As for one who joins the prayer late (masbūq), he only completes what he missed, based on the Prophet's (peace be upon him) saying: "Whatever you catch, pray; and whatever you miss, complete." There is no basis for a latecomer to perform the prostration of forgetfulness merely because he joined late.