A lot of the time when a cars performance is off, the first thing that gets blamed is the motor for not making enough power.
It’s usually when it’s not a “known good” combo, and/or has never been on the dyno.
In that situation you don’t really know what it “should” run.
If you have a bunch of 700hp parts, and your motor makes 700hp...... you’re doing okay.

One thing to keep in mind is, many combos don’t have another “easy” or cost effective 50hp in them.
The pre-disassembly dyno test can save them a bunch of money if the motor combo is already nearly maxed out.
Going from that 700hp to 750hp might require new heads, more cubes, a better block, etc.

Sometimes that next 25-50hp is way beyond what their budget is....... and what money they can spend would often be better spent on other areas, if the car isn’t running numbers that equate to what the motor is making for power.

In a situation like where the OP is at now, dyno testing the motor is part of the diagnostic process.
Just like when your “check engine” light in the dash comes on.
You can hook the scan tool up to it............. or start swapping out parts hoping the light will go out.