Right, but this thread was/is headed in the same direction as all oil threads which basically say oil/ratios can make or break an engine. The reality is the "testing" which was done to make that claim has far too many variables and lacks controls to be able to make a blanket statement like that.
The original post asked about stihl ultra and newer FD formulations. I'm a single data point and am saying I've exclusively used HP ultra at 50:1 with 87 octane ethanol enriched gas for 10+ years and not had a problem. This is with a br600, an fs90, and an MS290 beater saw which I know isn't 4 mix. Factory jets, approx 1k elevation.
Is it the fact that I let my machines warm up before hammering them? Is it that I let them idle for a few before shutting them down to cool the valves off? Is it that I keep the valves adjusted regularly? IDK.
But my point is that I personally believe if you use HP ultra, mix it to 50:1, and use the equipment with some care and common sense you won't have an issue.