How does giving Scar extra abilities in this fight demonstrate a lack of understanding regarding the Yautja?
You're missing the point, Ronan.
If the guy had actually demonstrated some understanding of the Yautja as he claims to have seen the films, read the novels, played the games-- then he wouldn't have had to give Scar any of these unneeded upgrades. In his writing, he doesn't demonstrate any mentioning of the metals used in forging Predator weaponry, he assumes that they need to be coated over with adamantium without any forethought that merely forging them to a molecular level would've allowed Dlex material to at least perhaps rival adamantium. And he doesn't take into consideration to what the Yautja can do or what their potential can lead them to becoming on their own.
So far, this just seems like your average run of the mill match.
This is still Scar. He is still armed with Yautja weaponry, still possesses Jehdin training, and still possesses the strength, speed and agility typical of a Yautja of his age. The difference is that his weapons and armor have been given a major upgrade, and his memory is gone: that doesn't change him into a completely different character. I could destroy Spider-Man's memory and give him an adamantium skeleton and claws, but that wouldn't make him Wolverine: he'd be an amnesiac Spider-Man with claws.
By that logic, I suppose Michael Bay's Teenage Alien Ninja Turtles are still Teenage Mutant Ninja Turtles.
The point of this is, you can only go so far as to adding to a character to the point where the character becomes unrecognizable. Do you understand what I am saying with this?
Taking your point with Spider-Man, here is another scenario.
As a matter of fact, let's take Batman and let's say he has been bitten by a Radioactive Spider, and decides to ditch the Bat-costume and instead chooses to make a spider themed costume to go in according with the theme of his arachnid powers. Then that's not Batman anymore.
Basically what the writer has done really was just take Scar before the events of Alien vs Predator, and change for the most part who he actually is. He was implanted with memories believing that he was part of a special operations group (presumably Weapon X) and was given a artificial healing acceleration (James Howlett/Logan/Wolverine), and was given Adamantium weapons (Wolverine).
My point is you can only add so much before it starts taking away of what was the original character to where it becomes unrecognizable.