Patryn of Elvenshae said:
Honestly, I've never imagined any other way to read that line.
It all comes down to how you read the "after making a successful grapple check".
If you include an implicit "to damage the opponent" in that sentence, then it makes sense for the claw damage to replace the unarmed strike damage.
But if you don't, there are a couple of other ways "after making a successful grapple check" is read. One is "after succeeding at a task that requires a grapple check" - which means it triggers if you successfully pin, if you successfully break a grapple, if you successfully retrieve spell components, and so on. The other is "after beating your opponent in an opposed grapple check", which covers all of the above, plus successfully resisting a pin, preventing them breaking the grapple, preventing them retrieving spell components, etc.
Now, if we read "after making a successful grapple check" in either of these ways, we have the following:
Without Improved Grab:
Pin: pins opponent.
Retrieve spell components: retrieves spell components.
Break grapple: breaks the grapple.
Damage opponent: deals unarmed strike damage.
With Improved Grab:
Pin: pins opponent, plus claw damage.
Retrieve spell components: retrieves spell components, plus claw damage.
Break grapple: breaks the grapple, plus claw damage.
Damage opponent:
deals unarmed strike damage, plus claw damage.
... does it make sense in this case for the damage opponent action to lose utility, unlike all the other actions? It doesn't, so it should still have its normal effect - deal unarmed strike damage - in addition to the claw damage.
I personally read "after making a successful grapple check" in this context to mean "after making a successful grapple check to damage your opponent", which means that pin just pins, and break grapple just breaks the grapple, but damage opponent replaces poor non-lethal unarmed strike damage with savage lethal natural weapon damage - a clear benefit to taking the damage opponent option.
But if you take one of the broader readings, damage opponent (without unarmed strike damage) becomes pointless, because every other option requiring a grapple check does everything damage opponent does, plus more. If the unarmed strike damage remains part of the effect, however, there's still a reason to choose that option.
-Hyp.