Ruling on a wife following her husband in his regular voluntary prayer while she is performing her obligatory prayer?

A person says: Often, after the prayer, he comes to his house and prays two rak'ahs with his wife, which are his regular voluntary prayer, and the wife completes them as her obligatory prayer. Some people criticized him and said: The congregation in voluntary prayer is not established except rarely, so do not do this often. What is your opinion, Your Eminence?
Leaving this off is more preferable, because this is what the Prophet (peace and blessings be upon him) used to do: him praying his regular voluntary prayer for himself and her praying alone is the best, as the Prophet (peace and blessings be upon him) did. When he came to his house, he would pray his regular voluntary prayer alone, and the women would pray their obligatory prayers alone. This is the best. If she prays with him while she is obligated and he is offering a voluntary prayer, it is valid, just as Mu'adh prayed with his companions while he was offering a voluntary prayer and they were obligated, and the Prophet (peace and blessings be upon him) prayed two rak'ahs with the second group in the prayer of fear while he was offering a voluntary prayer and they were obligated. There is no harm in this, but it is more preferable for the woman to pray alone and for him to pray his regular voluntary prayer alone, as the Prophet (peace and blessings be upon him) did.