Maybe some guys don't want to believe it, but Ruger buys parts and mags from several suppliers (at the same time). Ruger's Supply Chain does not put all their eggs in one basket - this is a "Risk-Mitigation Plan". Checkmate and Mec-Gar are only two 1911 magazine (lowest-bidder) sources, as there are more than two approved for this common part. Magazines are received, weight-counted, stored in bins, and delivered to the assembly tables as-needed just prior to function and test-fire. Its not rocket science.
Hence, there were multiple suppliers' lots available from 2011 to 2014 - and still are? Same goes for internals and grips, although if you really want to get anal like some quasi-collectors enjoy - several SR1911 models are/were sold to distributors without grips at all, so that those distributors can install special and unique grip panels themselves, when approved by Ruger.
I think some would be surprised to learn the gun-parts community is very intertwined and the extent to which everyone sells parts and processes to everyone else. "Make-or-Buy" manufacturing economics 101.
One thought - with ITAR regs, Mec-Gar and others sell from a US-based catalog or warehouse, so likely every part is "USA sourced", to make ad-copy claims legit.
And yes, Ruger execs do shoot locally, from Gunsite to CVSF to the now-defunct PSR (and they live & raise families here). No big secret. It is a rural community.