In D&D 5E, normal Two-Weapon Fighting lets you use your bonus action when you’ve used your action to Attack. It says:
You don’t add your ability modifier to the damage of the bonus attack, unless that modifier is negative.
The new Tasha’s Cauldron subclass Soulknife has a feature where you can create a blade of energy and attack with it, and that says:
After you attack with the blade, you can make a melee or ranged weapon attack with a second psychic blade as a bonus action on the same turn, provided your other hand is free to create it. The damage die of this bonus attack is 1d4, instead of 1d6.
It looks to me that while this is similar to Two-Weapon Fighting, it is not that same, and the normal bonus to damage would apply. Am I right?