गोविन्द भाष्य (श्रील बलदेव विद्याभूषण - अचिन्त्यभेदाभेद वेदान्त ब्रह्मसूत्र भाष्य सटीक)

They are different because of different words and other things.
Purport by Śrīla Baladeva Vidyābhūṣaṇa
There are different kinds of worship for the different forms of the Lord. For
each form there is a different kind of worship. Why is that? The sūtra explains:
"śabdādi-bhedāt" (because of different words and other things). This means,
“because the names of Lord Nṛsiṁha and the Lord's other forms are different, the
mantras for worshiping these forms are different, the forms themselves are
different, and Their activities are also different". In the Smṛti-śāstra it is said:
kṛtaṁ tretā dvāparaṁ ca
kalir ity eṣu keśavaḥ
nānā-varṇābhidhākāro
nānaiva vidhinejyate
"In the Satya, Tretā, Dvāpara, and Kali yugas, Lord Kṛṣṇa appears in different
forms with different colors and different names, forms that are worshiped in
different ways."
In this way it is proved that the Lord's different forms are worshiped in
different ways.
Adhikaraṇa 31
The Steadfast Worship of the Lord
Introduction by Śrīla Baladeva Vidyābhūṣaṇa
That the forms of the Supreme Personality of Godhead, beginning with the
form of Lord Nṛsiṁha, should be worshiped in ways that are different for each
form has thus been described.
Saṁśaya (doubt): Must the worshipers of these various forms meditate on all
the Lord's forms together, or is such meditation only optional?
Siddhānta (conclusion): In the following words the author of the sūtras gives