he's sort of right.
the blood crusade carved a bloody swath through the galaxy but lost momentum on two locations, the first was octarius where it got BTFO by the daily ork/nid continental monster mash at the equatorial line, by all accounts the crusaders were having a hell of a time but they were also getting fucking crushed before getting swept elsewhere by the blood tide.
the second time the crusade got stalled was by the saim hann eldar, who basically spent the entire duration of the tide skimming over their heads at supersonic speed hacking into them with blade and shuriken.
the forces of the crusade weren't fast enough to actually fight them for more than a few seconds with every flyby so they got frustrated and fucked off.
funnily enough the eldar saved the random imperial world under attack from the crusade by drawing the crusades fire like that, and fucked off immediately after, leaving the guard detachment scratching their heads wondering what the fuck just happened.>TL:DR Pic related but with world eaters.