Is this remanufactured ammo or from some small loading company rather than "factory?"
If so they are probably buying economical bulk bullets if the blt isn't identified. I haven't been loading ammo since about the time of the big ammo shortage but the cheapest domestic .224 55gr PSP blts were Rem, Win. and sometimes Hornady. For performance those are going to be pretty equal cup/core blts if loaded the same.
Now if they are going with some of the generic (especially fmj) blts being offered by some places I'm suspecting they are not domestic and don't have a clue but have seen some that were IMI.