There's some truth to the fact that Wal*Mart gets different/custom models and variants from the various mfg's. But only because of thier VAST marketing clout.
But I've been over the issue as well in other forums and you are right, low-quality el-cheapo's they aren't.
It would probably be more expensive for an established firearms company to disrupt thier line to downgrade thier QC rather than just run off a normal "high quality" batch.
The one example I can actually think of is Mossberg, and they actually set up another name/company, Maverick, and a plant in Mexico (IIRC) to do it, so thier cut-corners basic value line wouldn't detract from the reputation of the main Mossberg line.
Now just let W's little tax-rebate come before they sell out!