Firefox is too self-restricted in GPU memory usage

On iGPU hardware, default dedicated VRAM is usually 0.5GB and the maximum is 2GB. On my laptop Firefox only use 0.48GB(dedicated VRAM)/0.2GB(shared VRAM) when I set VRAM to auto(512MB) in BIOS. The screenshot is when I set dedicated VRAM to 2GB in BIOS, and you can see the VRAM usage has increased to 1GB(dedicated)/0.5GB(shared). It seems Firefox is restrict itself to dedicated VRAM and not fully utilize the vast amount of shared GPU memory. This makes sense on dGPU hardware but not on iGPU hardware. On iGPU hardware, the negligible amount of dedicated GPU memory exists only for compatibility to legacy programs, and Firefox should allocate all it's GPU memory from the shared GPU memory pool.