Virtualization is a specialization of emulation. to emulate something merely means to imitate. virtualization is still emulating a secondary PC environment. Saying virtualisation is not emulation is just fudging terms because people don't like the implication that the term "emulation" has. I recommend reading WINE's FAQ where even they admit that it would be more accurate to say "wine is not just an emulator". Virtualization is just a subclass of emulation.

most virtualisation software use API forwarding for 3D acceleration APIs

this is a common misconception Most VMMs emulate GPU. virtualbox, vmware, wsa, and qemu all emulate GPU (or rather, technically a gallium driver) for opengl support on linux and even windows. as windows guests under virtualbox actually uses gallium nine/dxvk under the hood (perf is still crap somehow though). the technical breakdown for qemu would be [ host gpu <--> gallium <--> opengl <--> qemu pipe <--> virgl <--> gallium calls <--> opengl <--> application ]

vmware/vbox are slightly different as it's an accelerated backend to vmgfx but that too emulates a gallium backend on linux meaning it's doing ogl -> gallium -> ogl etc.... Hyper-v/wsa is the exact same situation as both. I don't believe that bluestacks and memuplay deviates from this greatly. though it's not something I have looked in depth into.

it wasn't until recently with virglrenderer venus for qemu/crosvm and hyper-v gpu-pv that we have gotten real API forwarding for VMs (technically android's cuttlefish also had it IIRC, but preformance was terrible when I played with it, hyper-v also had something but it was really bad too).

as for other forms of api forwarding, qemu-3dfx is a prime example of real "api forwarding" to an extent, rather it forwards 3dfx and opengl calls to the host. and you can have d3d support via wined3d.