Notably, I have NVM setup to auto init on a work MBP and two personal Linux laptops before, on Antergos (Arch) and CentOS (on a very old and slow laptop even),

Notably, I have NVM setup to auto init on a work MBP and two personal Linux laptops before, on Antergos (Arch) and CentOS (on a very old and slow laptop even), and terminal startup time is still near instant in all cases. Issue was definitely isolated to WSL in my experience.