I believe so, yes. Keep in mind FidelityFX is a software-based solution so it can run on pretty much any compatible GPU. DirectML is a hardware-driven/accelerated solution that is meant for machine learning. It isn't exclusively for image resolution scaling, but that can be one of its uses.
So, theoretically there's no reason why it can't be used alongside FidelityFX for image resolution scaling purposes. In the same way, those can both be used along with VRS 2.0 as needed.
Here's an
official briefing for more info on DirectML.
I think the general worry (whether they're rightly or wrongly thinking of it is up for debate
) for some people when someone brings up the fact that, yes, Primitive Shaders were in RDNA 1 and even Vega cards, is that they think the person doing so is trying to suggest PS5 is RDNA 1.5 or something like that. Which just isn't true at all.
While some people thinking there are absolutely zero differences between whatever version of Primitive Shaders the PS5 uses (which just for clarity, is at least based on the updated spec AMD made, probably with further alterations from Sony) and Mesh Shaders are similarly wrong for thinking that, overall I really can't picture Sony having made such a mistake to not ensure their Primitive Shaders are at least comparable to the newer Mesh Shaders in terms of what they can do, even if there are some small idiosyncrasies between the two.
Considering what a performance boost Mesh Shaders will give to graphics pipelines when they are more fully supported by the industry, and that Sony want to support the PC platform more going forward, there's just next to no chance they haven't done work to ensure their Primitive Shaders are more or less up to par with what Mesh Shaders will provide, small differences here and there notwithstanding.
...although it'd be nice if they talked a bit more about their design openly. Kaz and Ken were good at that.