Is it really shooting itself in the foot, though? There are plenty of FOSS projects that companies benefit from and never contribute back to, either monetarily, or in the form of writing code. They provide an easy option to make it look more professional while helping to support the project, and you could always fork it and do what you need to with your fork. The idea that developers should do a thankless job to maintain their software in a way that complies with random corporate policies in order to be more widely adopted strikes me as setting up devs to burn out and crash from having all the joy ground out of their projects for them.

UNESCO, the Wikimedia foundation and other major organizations have already implemented it and gotten onboard, so I would suggest your coworkers are being a bit foolish in completely disregarding it because of a single mascot image that has a clear option to replace. The Dev is just saving themselves aggravation from people that were going to make endless demands of them, but most likely balk at actually supporting the project to enable features that only matter to their organization, but not to the Dev themselves or others.

I mean, you also acknowledge that cashiers are human beings and let them do wild things like have a stool or chair to sit on, or drink water as needed. As a country, the US has already shown itself to lack the necessary consideration and decency to let us leave these companies to their own devices with something like self-checkout. They will unfailingly select to most inhumane, awful way of implementing something that maximizes their profits at the cost of dehumanizing their employees and customers, while degrading the service they offer.