You see, people who are making their own cryptos are usually not the fans of Bitcoin and other major currencies. They can see how Blockchain can be profitable and want to utilize it for their businesses, but they also want to stay in control. Facebook banned crypto ads before announcing their own project, let's not forget that. At the same time, Jack has been an admirer of Bitcoin and things related to it (for instance, he tested the LN if I remember correctly). So if he wants to adopt some crypto, I don't think he'll make a token, I think he'll use Bitcoin.
If that will be the case, then it would be good for Bitcoin but I think Jack Dorsey and Twitter executives would find an ingenious
way to better monetize their platform instead of adopting Bitcoin yet I admit that it could also be a possibility and if this happens,
then the crypto-community would surely rejoice if they would integrate Bitcoin into Twitter. Imho.
I think because of many of us lack the knowledge of blockchain technology in adeptly including me is why we think that a company has to create its own cryptocurrency, one thing we need to know is that twitter is already a big company and they have money already, if they will want to get involved in blockchain technology, they are only doing so to better their system not because they just want to start making money for them to develop the project.
There is nothing wrong in them using a single currency that is assumed to be global and independent, it is not like every other cryptocurrency that has its ownership, but it is more like an independent coin that does not belong to anyone, so if they are building bitcoin, they are also doing so too for themselves.