Luffy and Loki's joint attack definitely packed more kinetic force than the trio's attack with Hajrudin IMO, most likely even by an order of magnitude more.
I’ll explain my logic using the Oreshnik missile (or any other IRBM or ICBM) so it makes a bit of sense: This particular missile hits (or impacts) at Mach ten kinetically, or a little bit higher if I remember correctly. If a conventional payload is added and it explodes just before impact, the destruction is increased by orders of magnitude, perhaps between two to three orders of magnitude which is between 100 to 1000 times more powerful, since the exploding force naturally inherits the initial Mach 10 speed as its starting point.
Perhaps it’s not exactly the same thing going on here, but Luffy’s mid-flight lunch of the dawn bullet while already travelling at such insane speed (due to Loki)… most definitely compounded the speed and impact of the attack, especially since it arrived with both conqueror's haki and the lightning, at least that's how I see it.
To add to your analysis, Sovereignty is like an anti-army or anti-fortress attack from Fate/Stay Night. It's meant for widescale damage, but because of that, the majority of the force is just wasted. Like if we pictured it as a wave attack, it's much larger than Imu, so Imu for example, only took 20% of the wave. Also, it being so big makes it theoretically easier to block with a single barrier.
Now, if Luffy, with a fully elastic body, is swatted, he's benefiting from what makes bullets so dangerous. The full force of Loki's muscle strength plus the force from the hammer is transferred into Luffy, and he delivers it to a single point. The same barrier that might have tanked Sovereignty had all of the barrier's face take a percentage of the attack and disperse over that surface.
This is the physics of why a hammer can't do significant damage to a block of wood in the same swing that sends a nail deeper into the wood.
It's the same physics as how someone might fall through ice if they stand, but can move across the ice if they're lying with their whole body.
Regarding your first opinion, I would say that the trio attack
could have had more kinetic force than this one, but the majority of the force hit empty air, and that will be true unless someone can show me an instance where the attack was concentrated on a head-sized point.
