Hmmm. Has this understanding been confirmed via WOJ?
I could be remembering Changes wrong but as I remember it that was pretty well spelled out as what the point was.
And while your point about the strength of the LoON and Red King are true--they had no idea where Eb would be and have no idea what his defenses are. If he was sitting in Edinburgh--which he would've been, if he hadn't come out to fight with the Gray Council, since the Duchess Ortega had called a conclave and whatnot--then they've got to get past the layers and layers of Sidhe and White Council wards sticked onto it for so long before they ever get to Eb's personal resources. If you have just one bullet to use, you make sure it's big enough to do the job.
But we're off topic. Either way--the original point was that blood bypasses thresholds and protections. My point is I wouldn't judge it a complete catch-all, but it is a powerful starting point and will take you a long way there where without it you'd be looking at something that's impossible.