It is because this is Onivim version 2. The first version was based on VScode, which was not native. You also didn't quote the important part. It should reads

It is because this is Onivim version 2. The first version was based on VScode, which was not native. You also didn't quote the important part. It should reads like this > the quick and responsive feel of a native app, and the vast extension ecosystem of VS Code. Essentially, you are in the market for onivim if - You like vim - You hate the sluggishness of VSCode - Your workflow depends on specific VSCode extensions (may be because all your teammates use VSCode?)