Netboot.xyz can itself boot from USB, but it does not then boot arbitrary isos off the USB like Ventoy. That's what I meant by it's slightly different, it chain loads netboot images. I find that's what I almost always want to do with a tool like this or Ventoy, so it suits my (and probably many) people's needs. But yes, it's not an exact replacement.

You can add arbitrary netboot images, but I'm not actually sure how much it can do with no network at all.