Here's my observations:
Someone posts on TFL:
This MIM widget broke on my ZY 2000 9mm! If they'd have used a forged widget, I'd have a working gun.
Someone else posts on TFL:
This Forged widget broke on my SH 17 .40! Must have just been a bad part. Sending it back to the factory.
Basically, if a MIM part breaks, clearly that's because it's a MIM part.
But when a forged (or whatever other process) part breaks, they just got a bad one.
People, parts break. I've seen parts break that were made with all sorts of different processes. MIM parts, used in the proper way aren't any more likely to break as any other process.
Anyone who says they won't trust their life to a MIM part better stop driving cars, and flying in airplanes. The process is used in so many industries.
Having said that, OP bought something, and got a something different. That's just wrong, regardless of how the part was made.