Lots of people have reinvented the Hoxie bullets. In the 70s and 80s and perhaps later CEPCO (Controlled Expansion Projectile Company) filed a patent in 1973 and it was issued in 1975 for bullets with steel balls in them. I have two different 9mmP rounds by CEPCO.
I think the Winchester monobloc may be part of an ongoing effort by FN. The 2002 Winchester effort for FN was followed by the EP2 round for FN that was manufactured by GFL in 2004. Note that the steel ball in the Winchester round was replaced by a plastic ball.
I don’t know where this EP2 effort went, but the rounds are hard to find and I have not seen anything that looks like a follow-on.