A while back, designer John Eaves (who has a long history with creating the look of the ships and tech of Star Trek) responded to a question on his private Facebook group about why they weren't sticking with the older designs. He explained that they'd been given a directive to try to make the tech look “about 25% different” from the stuff from the sixties. When asked if this was a creative choice or a legal directive, he said legal. When pressed on how this could possibly work with CBS continuing to issue licenses for model kits, games, comics, and books to use the original designs he replied that he wasn't the best person to ask, as he didn't really know that much about the legal wranglings that went on.
This entire exchange was later deleted by Eaves, and a correction was issued clarifying that this had in fact been a creative choice to try and update the original 60’s designs to take better advantage of modern effects technology rather than any legal requirement of their various licensing deals. Several YouTubers, however, seized on Eaves's original statement and suggested that the retraction and correction was some kind of conspiracy to hide some kind of legal chicanery and/or fool fans into embracing a false canon, which is why it has continued to spread.
In truth, it's far more likely that Eaves simply misinterpreted instructions he was being given as coming from the legal department rather than the creative team and, since he's already admitted to not following the details of the legalities for their various licensees, simply didn't question it.