I just noticed this as well when examining the config file again, so sorry for that oversight.
However, this behavior seems entirely counterintuitive. I suppose it's true that no games use both FM Synthesis and CMS/Gameblaster for music simultaneously, so in that respect it makes sense to include CMS as an alternative option to the Soundblaster's FM synthesis, but it makes no sense when relying on 'auto' mode.
Auto mode proclaims that the type of OPL emulation is determined by the card selected with "type=". However, there is no SB card that would ever be associated with CMS as OPL type, or if there is in DOSBox, it's incorrect. Soundblaster 1.0 supported both OPL/2 and CMS, but obviously OPL/2 would be favored over CMS in auto mode. From Soundblaster 1.5 to Soundblaster 2.0, CMS was optional and not included on the card by default, so OPL/2 would be the only supported option. Soundblaster Pro 1 did away with the CMS sockets entirely, as far as I'm aware, only supporting dual-OPL/2.
Therefore, if you want CMS support, you have to go into the config file and change "oplmode=" to "cms" every single time you play a game with CMS support, remembering to change it back for Adlib/OPL3 games afterwards. This sort of defeats the purpose of 'auto' mode, in my opinion.
Perhaps I'm totally alone but I favored the old method of distinguishing CMS support from OPL support, only because of the inconsistencies in its inclusion on various SB cards, and the fact that it was a separate card prior to the SB's existence. It makes more sense to treat it this way and to allow automatic support without fiddling around in the config file every time you want to use it.