Yeah, I’ve heard that before (not just from LEGO, other companies do this as well). Hasbro does the same system (at least for Transformers) since most products are originated with the marketing teams, then once approved by corporate, they’re then sent to the designers to be executed. While the designers have a good amount of freedom in what they come up with, they are definitely given some level of restrictions to work with (LEGO probably does part count and characters for most themes, Hasbro mainly gives designers a budget for new molds to use on each wave of figures).
Lego honestly has more freedom for the designers precisely because of how many parts are reused. Recolors would be relatively easy to get added to sets because you don’t need new molds, but new parts are definitely an expense to be considered.