In the Sims 3, all hairs are alpha hairs because they make heavy use of transparency. Alpha CC / Maxis match CC only makes sense in the Sims 4, because Maxis hairs reduce transparency (alpha channel) as much as possible to give this blocky style that Sims 4 Maxis hairs have, which is much easier to render by low end computers on low graphics. Whether CC is 'Maxis match' or not doesn't matter in the Sims 3.

Otherwise, since aesthetic in The Sims 4 is so vastly different from The Sims 3’s more realistic character models and world assets, people will use these terms more loosely, and just to better differentiate the two types of custom content, because the majority of players tend to be either or, and rarely in-between. Technically The Sims 3 does have alpha hairs, so it’s terminology that’s used less in this particular community, but people will use custom hairs, but prefer a more “Maxis Match” texture on it, rather than a texture that looks more shiny or hyper realistic, so to better match the hairstyles already offered by Maxis themselves, and cause less aesthetic clashing. Maxis match cc = cartoony ( or whatever you’d call the original game’s aesthetic )

This term is used quite a bit in The Sims 2 community as well, as the sentiment began there ( could’ve been in the og Sims as well, but I don’t use cc for it, so I can’t be sure ). Maxis Match is whatever cc actually matches the game’s aesthetic, or only slightly improves it, so a lotta the time it uses the original assets, but will edit it a bit or mash it up with other original assets. Well alpha is more a blanket term that was adopted with The Sims 4, bc the official hairstyles in the game do not have “alphas”, it’s typically one big “mesh” or chunks with no see through strands, so it doesn’t look as real as actual hair, therefore alpha cc is basically cc that looks more realistic, and less cartoony like the game’s intended aesthetic.

The sims 3 toddler hair cc