"In particular" could also be interpreted here as just signaling the main subject of the article, not necessarily making any sort of claim to comparative amount of syncretism.
No, that phrase is just filler. And IMHO it's basically wrong. Certainly if the author want to show that Christianity is more likely than other religions to import ideas, the article has a lot more work to do than point out one myth. Literally everyone does this.
I'm just going to repeat: there is nothing notable or unique to Christian appropriation of myths and stories from other religions. It does it at least as much as everyone else does, and everyone does it everywhere. So trying to tie this uniquely to Christianity seems needless and confusing. The deeper point is more interesting and more important.
Is there anything in that paragraph you'd like to argue about?