I order multiple 100g bottles, and the last two times they've been in labeling unquestionably from a big company, just like the Spectrum glycin I used to get from Bryant Labs locally, or other kinds of specialty chem from scientific suppliers lately. Before that, PS bottles were different, primitively labeled with the detail sheet taped on, just like all their other house chem. But my last purchase was two years ago, and the glycin just thawed is still off-white, so has remained in excellent condition frozen. I dunno. Perhaps they fill in sometimes and formulate sometimes. But why would they go to that bother if there's a reliable industrial source? I'll order more from them in a month or so. Their glycin has been reliable; amidol not so (came from China).
More likely, you misunderstood what they told you : they measure out and bag their 130 kits themselves. Yes. But this doesn't
necessarily mean they make the bulk individual chemical components.