> There's a lot of examples of that, like it still being called Unleaded Gas despite it having been so by default for how many decades?

Depending on where you live, about 0.35 decades?

> On 30 August 2021 the United Nations Environment Programme announced that leaded gasoline had been eliminated. The final stocks of the product were used up in Algeria, which had continued to produce leaded gasoline until July 2021.

- https://en.wikipedia.org/wiki/Tetraethyllead#Modern_findings