Kurzgesagt is a channel that makes engaging explainer videos about all sorts of topics. It is run by a design consultancy in Germany. Most of the videos on the channel are not on topics chosen by sponsors, but a few are.
In an article at
https://medium.com/@Kurzgesagt/kurzgesagt-sponsorships-on-yo...
Philipp Dettmer, the founder of the channel, explains that he insists on editorial independence when accepting sponsorships to create videos on specific topics (including in this case, with the Gates sponsorship). This seems to suggest that the Gates Foundation did not choose how the video would be titled or promoted on YouTube, just that it entered into an agreement that it would sponsor the creation of an engaging video about vaccine risks and benefits.
I don't know if anyone at the Gates Foundation specifically thought about the question of whether simply mentioning this topic in a certain way would encourage some viewers to think that the risks were worse than they are. Even if so, it's not clear that they would have a veto according to their sponsorship agreement.
(The article also indicates that people can also hire the team behind Kurzgesagt to make videos to a customer's specifications. In this case, those videos don't appear on the Kurzgesagt YouTube channel.)