I'm pretty sure the virtual word here refers to the geometry being in a virtualized form, meaning that the renderer refers to it but the GPU does not have all of it in RAM but instead is paged in on demand.
This paper about geometry images[0] was mentioned on Twitter from an old post by the programmer who implemented the functionality in UE5. Geometry images encode geometry in rectangular 2D textures that can be reconstructed later (the paper is kinda old for this, but i guess it can be done on a computer shader nowadays). If those images are stored as virtual textures, which are supported by the GPUs nowadays, they could be essentially using sparse textures/resources to store geometry.
This paper about geometry images[0] was mentioned on Twitter from an old post by the programmer who implemented the functionality in UE5. Geometry images encode geometry in rectangular 2D textures that can be reconstructed later (the paper is kinda old for this, but i guess it can be done on a computer shader nowadays). If those images are stored as virtual textures, which are supported by the GPUs nowadays, they could be essentially using sparse textures/resources to store geometry.
[0] http://hhoppe.com/gim.pdf