When a lubricant is developed to create a synergy with a specific engine for specific conditions, nothing hurt to work on enhancing the lubricant abilities if there are none fitting the needs for the engine you use...200ppm of Antimony addition is not a lubricant development that requires a real lubricant development...
Long time I didn't post on here...
Oils are a balancing act, performance improvement in one area can negatively impact another, this is why extensive testing is done to ensure the efficacy of formulation changes and component selection. Dosing that carefully balanced chemistry with another component, be it an EP additive, FM, thickener, cleaner...etc. WILL have an impact on the performance of the product, and the odds of that impact being overwhelmingly positive are impossibly remote.
This is something I've discussed with Dave at
@High Performance Lubricants quite extensively. Each additive package and base oil blend responds differently to different FM compounds and compound combinations. While a full-SAPS A40 additive package in a 0W-40 might respond best to a 60/40 blend of trimer/dimer moly and not respond well to additional augmenting with say titanium, an API SP/dexos additive package might respond best to a 10/80 blend of trimer/dimer moly and a 10% dose of titanium. Or a mid-SAPS C40 additive package in a 0W-30 might respond best to a 80/10 trimer/dimer blend with 5% tungsten and 5% antimony. I'm pulling these numbers out of my posterior, but the message here is that different suites of additives, in concert, respond differently to additional components and the base oils, PPD's, VII's and other components also influence this. That's what full formulation is all about.
Now, you are less likely to see some of these compounds used in OTS lubricants due to cost, and it's not unusual to see the same additive package recycled across different grades and base oil blends also due to cost. TEOST restricts moly use for example, as we've recently discussed, but in the context of your "best available oil", these restrictions and cost cutting aren't in play.