Is it permissible for someone who missed a rak'ah to prostrate with the imam if he finds him prostrating, or should he wait until the imam rises?

If a worshiper arrives while the Imam is in any position, he should join him. If he finds him prostrating, he should say "Allahu Akbar" and then prostrate, based on the Prophet's (peace be upon him) saying: "(What you catch, pray, and what you miss, complete)." Also, because this prostration might be a reason for the forgiveness of his sins. The worshiper prostrates, then stands up with the Imam. This prostration does not count as a rak'ah, because a rak'ah is only caught by catching the bowing.