Look, I hate this as much as the next guy, but there is a use case for this. It is a frustrating use case, because it is for players who are not playing the game correctly, but it is not just 'Wizards is a greedy evil company that wants to make every game D&D'.
There is a Type Of Guy who wants to play the exact same character in every TTRPG they play. I don't mean "they always play a spellcaster" or "they have a thing for dwarves" or even "they get pissy if you try to make them play a TTRPG that isn't an OSR setting"- I mean they want to play the exact same guy. They insist that they always play Dzzyyt'rklk the Drow Ranger, regardless of whether they're playing D&D, GURPS, Shadowrun, or Call of Cthulhu. It's like their fursona.
This Type Of Guy is most common in D&D because of aforementioned homogenization, but he sure as hell exists in V:TM too. (There are less of them, but the ones that exist are louder and more annoying about it. The LARP angle does not help.)
If you are a DM running a D&D home game, because you want to play with your friends and most of your friends play 5e and don't want to play VTM, and one of your friends is That Type Of Guy who always wants to play his fucking fishmalk in every fucking game, and you don't want to exclude him because he's a great guy, he's just got this one really annoying habit... You basically have three options.
You can tell That Guy "no, you can't do that, and if you keep insisting on doing that you can't play anymore." You can try to work with him to find a concept that will work within your setting that lets him translate the character over. Or you can try to make some godawful homebrew cludge that lets That Guy have his exact character, game engine be damned.
This gamebook exists for DMs who would rather choose Option 3 (and thus preserve harmony at the table) than set a boundary that could upset a friend.
...It's also not a Wizards product or part of their ~Brand Strategery~. You notice, this is made by an indie team? 'Officially licensed' means 'we got permission from the rights holder and/or paid them some money so they don't sue us to oblivion'. It's sold on DND's official marketplace, because that's where you go to sell stuff to 5e players. This is not a WOTC product. It is barely produced under their auspices. The guys who made it paid money to Wizards and whoever the fuck owns VTM now so that they wouldn't get sued to hell.
Do I like that that gamebook exists? Of course not; I'd rather more people understand how RPGs work and play them accordingly! But I can't fault anyone for not wanting to deal with a huge amount of drama over something that is, functionally, a leisure activity. And making a homebrew VTM/DND cludge is a nightmare that no DM should have to do. The indie team who made this book is trying to solve a real problem; it is a problem that shouldn't exist, but they are trying to do something helpful for the community.