Jorg Kennis shares his knowledge about why the CD-i 180 player does not accept regular CD-i pointing devices and speculates about why it is different from the rest: Jorg: "CDI-180 pointing devices are specific for the CDI-180 (exception is the infrared remote: the CDI-180 supports Enhanced RC5, and hence can use the Thumbstick remote, and the RC5-supporting players like the CDI-205/910 can use the CDI-180's remote - for pointing only, the numbers and other keys do not work with the consumer players, more on that below). You are right that a preliminary version of the CD-i spec (Green Book) was ready by the time the CDI-180 was launched, however be aware that the specification for the connector and data signal were never part of the Green Book. The Green Book only specifies what a controller should be able to do (X/Y, two action buttons), not how it should be connected to a player.
Philips published a tech note specifying this connector and the data for other companies to use. This "Technical Info Pointing Devices" can be found here: http://www.icdia.co.uk/docs/index.html. As for why this specification was only used for all players starting with the CDI-60x, and why it is not based on the connector and data signal of the CDI-180, I can only speculate. The CDI-180 was developed in co-operation with Kyocera, perhaps they reused technology that Kyocera already had in house, but did it not meet some requirements that they added later. I know for a fact that the mouse is similar to the mouse of MSX computers (popular in Japan back in those days), me and some friends even replaced the 9-pin D-Sub connector of MSX mice with the round DIN-pin of the CDI-180, and that worked. Not sure if that would also have worked for devices like joysticks. You could not do this for consumer players, the data signal, as described above, was different by then.
Also interesting: The first Sony player (IVO-V10) did not work with the "Philips spec" pointing devices, but the revised model (IVO-V11) did. Infrared remotes where not specified at all in the Green Book or in separate Tech Notes. The RC5/RC6 standards were Philips specific (for the Thumbstick and Commander). Philips based players from other brands of course also worked with these remotes. I'm not sure what infrared standard LG/GoldStar used, but they might have licensed the RC5/RC6 standard."
[Thanks, Jorg Kennis]