First off, I'd like to say that the WBC doing this is ridiculous and shows how little credibility they have. However, there is a lot of misinformation out there being published by people who fancy themselves to be journalists about what the decision means. Based on the information the WBC has provided, it is not like the WBA Super/Regular like some of those "journalists" have stated. The "Franchise Champion" is not an actual title. Canelo has vacated the legitimate title and Jermall Charlo is the legitimate WBC Middleweight champion. This was very likely a PR move to distract from Canelo vacating the belt because fighting Charlo as a mandatory wouldn't happen for various reasons.
Reading the ruling (https://wbcboxing.com/en/saul-canelo-alvarez-wbc-franchise-champion/):
"2. This designation is not transferable and is exclusively to the fighter who receives such designation."
"7. The WBC may award a Diamond Championship belt in those fights in which the Franchise Champion engages. If the Franchise Champion loses, the winner will receive the Diamond belt and may be considered as mandatory contender of the division."
From this, we can see the "Franchise Champion" status cannot be transferred, i.e. it is not an alphabet title. This why they are saying they may put up the "Diamond belt" (whatever that means) and if the "Franchise Champion" loses, the winner becomes the mandatory to the WBC title, because the "Franchise Champion" isn't an actual alphabet title. Jermall Charlo is now the legitimate WBC Middleweight champion which Canelo vacated.