Stating the obvious for some of us who repair CD-i players a lot but this little bit of trivia is a nice thing to uncover: When tearing down a CD-i 910 (or 205, which is exactly the same unit) and place it right against a CD-i 604 or 605 (without the case) - You'll immediately recognize the similarities: The inside case, the metal housing holds the same design, it was actually used for both models. CD-i member DrChesterton pointed us towards this hole in the metal housing of the CD-i 910/205 on the right part, why was it in here? It appears that the same hole was used with a fan in the 604 and 605, probably as the components were generating more heat inside a professional CD-i player.
Below you'll see the CD-i 205 (910) without the case. Notice the position of the components:
Below is a CD-i 604, without a case: You can see the ventilator on the bottom right.
A more closer look at the hole+fan of the CD-i 604:
[Thanks to Retrostuff for pointing this out, Dr Chesterton for his question]