It's not that Shirou had trouble copying his skills exactly, it's that Lancer was a demigod with a superhuman body. He could reproduce the skill just fine... But he'd rip his muscles apart doing so. That kind of logic.
One world magecraft style....
I'm going to head-canon it that just like Gilgamesh was the King of the World ruling a planet-spanning super-civilization instead of ruling a few cities in one valley between two big rivers; like that, King Solomon is also "somehow" the cultural ancestor of all magi everywhere.
I don't know how that will fit in with the Babel myth, but the Noah-flood story is just a reskin of the Utnapishtim Myth, plus all that cosmology in Genesis that was a pretty direct copy of Akkadian-Babylonian lore; so there's already archaeological evidence allowing me to just conflate the Pentateuch with and Babylonian myth.