Given that at present there is a KNOWN issue with the AMD Drivers (and thus all GCN / RDNA Cards) on Unreal Engine 3 games., which is patched out in the Drivers that still supported Terascale Architecture... then I'm going to say BS., but even if we ignore the Geometry Culling that doesn't work on AMD Graphics that results in substantially lower (typically up to 50%) vs. the comparable NVIDIA Graphics...
There are still the issues of Micro-Stutter that were present in the DirectX 9 Version., became progressively worse with the switched to DirectX 10 and 11... which affect ALL Graphics Cards. Again, I'm going to have to say BS that you've had no issues in terms of performance on UE3 Games.
Unreal Engine 4 has also since launch had some notable performance issues.
And on AMD Graphics., it is common knowledge that comparable NVIDIA Graphics will have substantially better overall performance... this is reduced in the new DirectX 12 Path (now they've finally finished and released it) but there is STILL a clear degradation in performance in favour of NVIDIA., which keep in mind typically in DirectX 12 (or Vulkan) "Comparable" AMD Graphics will often have a slight performance advantage, provided Developers are Agnostic in their Optimisation Targeting.
The *ONLY* Unreal Engine 4 Games that provide AMD Graphics with a performance advantage are Gears of War 4 and 5... and actually today Gears 4 doesn't.
At Launch it did, because it Coalition did what most Studios won't do... which was rip out the entire Rendering Pipeline and Build their Own.
Now in fairness with Gears 4 they HAD to because Epic was refusing to continue Development of their DirectX 12 Integration; and Gears 4 *HAD* to be a DirectX 12 Showcase game for Microsoft Game Studios.
But that (on PC) was ultimately removed,.. I can't tell you why. All I can tell you is there was a patch... one Day it had DirectX 12, the next it didn't and instead suddenly was using Gameworks. Performance on AMD Graphics tanked... HARD, as well as introducing Frame Jitter that wasn't there before.
Gear 5 however while "Technically" uses Unreal Engine 4., it's actually a branched path and is heavily modified...
Once again an updated version of their DirectX 12 API is back (and is a damn sight better than Epic's implementation), but they overhauled a lot of that Engine.
Now while you can say "Oh but Microsoft uses Unreal Engine in most of their 1st Party Games...", that doesn't mean it's "Good" or even particularly good for their Hardware. Microsoft simply have a perpetual License due to their deal with Epic... it makes it cheap (well free) for them to use it., and it's generally "Good Enough" for what most Studios want to do, because well Graphical Fidelity and High Performance was never a major concern.
Rather what was, tended to be rapid development pipelines; which given Unreal Engine is a complete Workflow Pipeline, and Industry Standard... I mean it makes it somewhat perfect for needs.
I'd argue the ONLY reason Coalition are still "using it" ... is because Gears was born on Unreal Engine, and in fairness most of the guys there built the original engine in the first place; they know it probably better than the Epic "Old Guard" that are still left there.
Personally I think their Epic' Engines were better BEFORE they got in bed with NVIDIA and Tencent... clear there are influences and that results in them having a reputation for basically screwing over AMD Hardware.
And that's not just me saying that, it's well known. Digital Foundry FFS have done half a dozen pieces and technical reviews on this very topic.
They mention how it basically doesn't like AMD Hardware in every UE3/UE4 Game Review; which is likely why in the Gears 4 and 5 reviews they're massively surprised that Coalition was able to change that.
That has NOTHING to do with "Optimisation" that other Studios don't do, unless by that you mean basically rewriting large chunks of the Engine.
The last time a Developer rewrote THAT much of the Engine they were "Modifying" for their needs; we got Half-Life and the Gold Source Engine.
