`evil-org->` doesn't matter per se. It runs `evil-shift-right`, which indents the selected region by the `evil-shift-width` amount. `evil-shift-width` is set based on `tab-width`. I solved this specific problem by overriding `evil-shift-width` using a timer in an org-mode hook. The delay introduced by the timer was necessary, as something kept overriding my settings. Perhaps the magic machinery that sets `tab-width` in the source blocks can also set `evil-shift-width`. The best-case scenario would be to have a list of variables that need to be set from their major-mode buffer in the source blocks.

> May you please provide a detailed example where 8 spaces causes issues?

My lists are still indenting with 2 spaces, so I am not actually seeing 8 spaces. I have no idea why that is, but I very much like the 2-space indentation.

```
- a
  - b
```

I see 4 spaces in numerical lists, which again, I have no idea about:

```
1. hi
   2. hi
      3. hi
```

So I don't see the effects of `tab-width` anywhere except in `evil-shift-width`, as far as I can see currently.