The contention is/was that metal feedlips provide no benefit, not that you couldn't do it. And, they don't. Metal bends and stays bent instead of deflecting and returning to proper geometry. Proper polymer can maintain correct geometry and return to that after deflection, even if cracked. Plus, the dual material construction provides a variability that is more difficult to QC, metal feedlips provide more drag on the round/strip more energy off the BCG, mechanical adhesion of the two components can fail in the drop tests, etc. The steel lancer feedlips do provide some additional resistance to bending over USGI aluminum, though. It's not a terrible magazine, it has just been tested and found wanting in durability as well as in reliability. You may use Lancers for a few hundred or a few thousand rounds on the range, in typical range conditions, and have no issues. If it works for you, great. I get it...it would just seem to make sense that the steel feedlips would provide some benefit. It just doesn't test out that way.

The TOP tests aren't the same as what most folks test in YouTube videos. There are a lot of other drops and impacts, specifically full weapons drops, that are pretty hard on mags. The dust test is also a killer for mags with softer body compositions, like the Lancer.

The USMC chose the PMAG because in multiple rounds of testing at Aberdeen over several years, it was best. In the end, the GEN M3 PMAG was the most reliable commercial or government magazine tested by a very, very large margin, and passed all TOP 03-02-045 durability and environmental tests.  In the USMC tests, the Lancer L5AWM finished dead last, with multiple ammunition types in the test, not just M855A1. Those test results were published, and you can find them online. Later rounds of testing, including one round of tests that went to 250,000 rounds through PMAGs convinced Army to approve the SEP proposal and fully approve fielding the M3 with regular magazine funds. SOCOM approved as an authorized user when USMC did. AirForce adopted, as did Coast Guard and NSW. Last round of testing was over 30,000 rounds between magazine-related stoppages for the M3.

Richard or Magpul's "deep pockets" had nothing to do with selection, and he was an NCO, so he knows somewhere around zero general officers and influencers in the chain. Lancer's main business is aerospace and carbon fiber components, so their pockets are probably deeper. The USMC cared about nothing but data, and they are extremely happy with their decision.

London metro has pretty much ditched the Lancers due to reliability issues. They are now issuing 300BLK PMAGs going forward. Poland is going to M3. The Netherlands is ditching Lancer and going M3. Estonia looked at test data and chose PMAGs. The French tested and want PMAGs--although we'll see if HK strongarms them with the 416 buy. The Brits will continue with M3 after the EMAGs are gone. The data is hard to ignore, and coupled with a very satisfied USMC, and dissatisfied Lancer users, lots of folks are becoming M3 users, even if they gave Lancer a try.

There has been some confusion about MCT, also. FDE, the original tan color in magazines, provides some challenges due to the nature of the colorant in thin magazine wall stock thicknesses. It works just fine in furniture, but it was always a hair weaker than black in mags, and difficult to QC for that purpose. Every once in a while, you'd get one that was significantly weaker. That's why we discontinued it in favor of the "sand" color program. Sand uses a different material additive package to be stronger than black, and MCT, the new, darker tan, is based on the sand material. MCT is as strong or stronger than black. MCT was what was used for all of the USMC test mags, including the cold weather drops. Black was used in earlier testing. Both window and non-window variants have been in the government testing, performing identically within statistical significance. With the bulk of the USMC fleetwide fielding orders filled, and the US Army on a sustainable path for fielding, you will see MCT in other mags now, first up being the 20rd LR/SR .308 magazines.