Alexander Arms farms out everything they are assemblers and are not very good at that.
I recently was going through some upper receivers from various sources, squaring the faces of them before doing some accuracy builds with high-end barrels.
The Alex-A M4 upper was the only one that had a true receiver face, and also had a tight tunnel for the barrel extension.
I have also worked on several complete AA rifles for cerakoting, and they are some of the best-built AR15's I have ever dealt with. I've been avidly shooting, working on, deploying with, and living with AR15's/M16's/M4's since 1988.
Alexander Arms are big on patents and law suits. Bill Alexander likes to design things and expects others to make them on their dime and pay him for the idea. He had a big fallout with Starline(about Beowulf brass) and Saturn about Bolts and Barrels .He and LW were partners at one time and that fell apart. The bolt is a 7.62 x 39 bolt face AR bolt Rock River chambers a AR in this Caliber check with them.
No, Bill Alexander didn't want customers getting left out to dry with chamber variations, so he had anyone who wanted to make Grendel's sign and agree to a licensing contract that held them to the chamber standard before the cartridge received SAAMI approval. Once SAAMI approval happened after Hornady submitted it, all licensing and trademarks to the cartridge were released, since the manufacturers can look at the SAAMI drawings on their own now.
I've spoken with many parties personally that you have mentioned and more, face to face at SHOT over the years, and I can see what has gone on. It comes down to people not being able to swallow their pride and accept their mistakes. Some of the companies you mentioned are still making the same ones, and turning out crap product for customers to deal with.
One you didn't mention that is a good example is the old CProducts. Bill A. specifically asked for a curved magazine for the Grendel that was the same size as the 5.56 civilian 20rd mag. What did they do? Send him a pallet of straight 17rd mags, which you can still find on the market, that didn't function if you loaded more than 5-7 rounds in them. Bill rejected the entire pallet of them, and CProducts took them back. AA never carried that mag, and they ended up being sold to distributors all over, rather than being destroyed.
Worse has happened with barrels and bolts.
In any manufacturing market that involves multiple sub assemblies, it is standard for companies to rely on machine shops and specialty suppliers to provide parts and services that are in line with their core competencies. Nobody makes their own springs, detents, triggers, extensions, barrels, forgings, gas tubes, etc. under the same roof.
Not sure what your vendetta is with AA, but you didn't do much to hide it. Back story?