Enthusiasts who upgrade to Intel's Arc A-Series Graphics products will need to ensure that Resizable BAR is enabled if they wish to see their hardware running at their very best.
For current gens, it's hit or miss from what I've seen. I know that Hardware Unboxed from Down Under have benched with it disabled for a time, though not sure what their current opinion is as games and drivers have matured.
For Intel, it's probably a case of engineering ARC with the expectation that the function will be available.