[3.0] Removed all $that variables

| Q             | A
| ------------- | ---
| Bug fix?      | no
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | maybe
| Fixed tickets | ~
| License       | MIT
| Doc PR        | ~
Can we change the visibility of a method who are not flagged as `@internal`? (even if it seem to be used only in closure)