Basically, there was never a lot of detailed information about who manufactures chemicals for whom, nor is it really necessary. You rely on the owner/marketer/distributor to guarantee that the chemical is fit for use and that it matches the times on the chart. Freestyle clearly distributes a lot and owns or licenses some trademarks, and PSI (Photo Systems, ex Unicolor?) in Michigan appears to manufacture and possibly design photo-chemistry, but what intermediaries there are is beyond me - I don't know whether Freestyle owns the "Legacy/Eco Pro" name or just markets it. Freestyle has been around a very long time and is clearly dedicated to film, so I more or less just trust them to be suitable.
Even in the heyday of film, presumably the Kodaks and Agfas and Ilfords had chemical manufacturing and packaging facilities, but if you bought something from a smaller player like Edwal, or Diafine, or Heico Perma-Wash? Was there actually a chemical plant at the Heico office, or were they buying barrels of sodium sulfite from some larger plant, and they just diluted and bottled it? I dunno.
There has always been a lot of subcontracting in chemical manufacturing. If I buy a lab reagent chemical from Thermo Fisher Scientific, like say 99% hydroquinone (they sell it, but I'm sure it's more expensive than necessary for photo use), they'll provide a lot number and various certifications for it, but I don't know whether it came from a vat in Michigan or New Jersey or ? Equally, I assume that Photographers Formulary does not literally synthesize all the stuff it sells, or maybe any of it. They probably warehouse and package it, which is good enough for the darkroom user.