IANA pill expert, but just thinking about the mechanisms… basically you mix up a collection of medicine and filler - hopefully in a uniform mixture - and press it into a solid pill. if necessary, coat it with a “sealer”.
Think about the other manufacturing problems -
-if you put an “outer layer” like the candy coating on an M&M - if that’s the active ingredient, how do you ensure a uniform layer? For M&M or Reeses, if your machine messes up or your coating material is too viscous, the consuming public gets an small extra dollop of sugar and red dye#2; if the same happens at Placebin Pills, Inc. the public could be overdosing on 2 or 3 times the normal dose.
Similarly, dropping a smaller pill on a layer of larger pill, then pouring on the top coat - sounds good, but the centering procedure to ensure proper coating sounds difficult. If you then “press” to compact and form a pill, a mis-centered core piece may make one side of the pill dense and the other crumbly soft.
A 2-layer pill, like a twinkie or a jelly donut? You can’t really “inject” a hard pill with another hard pill, and if you inject or drizzle the medication on a sugar pill, now you have drying issues - I don’t imagine a lot of medications like being subject to high heat to speed dyring.
The other way would be to “layer”, which seems a bit simpler. Pour Mix A into the mould, flatten, pour mix B, compress into pill.
At the end of the day, though, the real question is “why??” Unless you have two separate ingredients that don’t play well together, so you have a 3-layer pill with the bufferin in the middle - why would you make trouble by making the manufacturing process, and the added quality control issues, that much more complex?
The only step I could see that matches the OP question is this:
Pour the buffer powder into the mould about a third the way. Maybe press it lightly into a bowl shape? Fill a full dose of medicine, then fill the pill mould with the rest of the buffer mix. Compress into a pill. The only reason to do this is if the cost of this 3-step process is cheaper than dealing with the issues around ensuring a pill-buffer mixture is uniform enough to ensure a consistent dose.
In any case, an unreliable distribution of medication in the pill would probably cause quality control issues.