If you're noticing that the numbers that form a list are right below each other in the same column, it kind of makes sense. Suddenly it seems a lot more ordered. Could be done differently though. Left alignment seems clearer:

  *ValueError: ExceptionGroup('eg', [ValueError(1), ExceptionGroup('nested', [ValueError(6)])])
  *OSError: ExceptionGroup('eg', [OSError(3), ExceptionGroup('nested', [OSError(4)])])
  | ExceptionGroup:  (2 sub-exceptions)
  +-+- 1 -------------------------------
    | Exception Group Traceback (most recent call last):
    |   File "<stdin>", line 15, in <module>
    |   File "<stdin>", line 2, in <module>
    | ExceptionGroup: eg (2 sub-exceptions)
    +-+- 1 -------------------------------
      | ValueError: 1
      +- 2 -------------------------------
      | ExceptionGroup: nested (1 sub-exception)
      +-+- 1 -------------------------------
        | ValueError: 6
        +------------------------------------
    +- 2 -------------------------------
    | Exception Group Traceback (most recent call last):
    |   File "<stdin>", line 2, in <module>
    | ExceptionGroup: eg (3 sub-exceptions)
    +-+- 1 -------------------------------
      | TypeError: 2
      +- 2 -------------------------------
      | OSError: 3
      +- 3 -------------------------------
      | ExceptionGroup: nested (2 sub-exceptions)
      +-+- 1 -------------------------------
        | OSError: 4
        +- 2 -------------------------------
        | TypeError: 5
        +------------------------------------