Could it be that macOS reports GPU memory as main memory on M1? It would have been useful to look at the GPU memory usage on the Intel test.

I don't know much about the M1 graphic stack, but I remember being able to malloc a buffer in the userspace and passing to a Metal kernel as a texture not so long after Metal was announced.

I imagine that on the M1, the driver asks for a chunk of the main memory to the kernel, whereas on Intel the driver asks the GPU to allocate a chunk from the GPU memory.

Likely a bug with Safari's Rendering / GFX Stack or the M1 GPU Drivers. Since using Chrome on M1 or Safari with Intel iGPU using System memory as Graphics memory doesn't share the same problem.

Pardon me if I'm wrong, but would this happen because of the unified memory on the M1 architecture? Since the CPU and GPU share the same memory, their combined usage would be reported.