Well, such explanation doesn't make a lot of sense.
You may want to add it if you want fully dinamic GI with day-night cycle and destructable buildings/etc, if you want subpixel geometry, if you want unifyed lighting solution without tweaking baked assests and scene lighting to death, if you want hightly customizable area lights with variable penumbra shadows, millions of lightsources in frame, etc, etc.
In fact, most of these things have already been implemented in engines with hybrid RT, such iterative development does make sense unlike sudden desire to move to path tracing just because it's "cool".
When devs are done with replacing rasterization based hacks and tricks with way more robust RT shadows/GI/etc systems, then they will start moving to the unified RT solutions, such as PT.
It appears that deferred engines still suffer from small triangles
They don't suffer during shading phase because deferred rendering does shading on full screen quad - no small fragments.
which is why Nanite exists and why there is a lot of work going in to visibility buffer techniques
Nanite exists to accelerate G-Buffer fill phase, i.e. rasterizing pixel sized triangles where HW rasterizers suffer, shading phase happens later on and has nothing to do with Nanite since it's decoupled.
UE5 still uses deferred rendering to shade the majority of objects on screen, visibility buffer is used to decouple draw calls from shaders so that Nanite geometry can be drawn with a few execute indirect calls, also visibility buffer is reused to shade custom materials later on.
I would tend to agree, but I suspect that's really a problem with older games/engines.
I guess it does not matter whether an engine is old or new, if it does tons of small draws and dispatches with 1*1*1 grids, it will work like ass on wide GPUs (on consoles that stuff is usually hidden in async, but that's not always the case on PC).
