Well there's one in the article, the colour of the floors.

My point about the buses is about "missing the forest for the trees", so the fact that you've focused on getting a specific citable example while missing the point is quite ironic.

Here's an industry article about the phenomenon: https://enotrans.org/article/a-bus-is-a-bus-the-costs-of-exc...

And here's a study documenting excess customisation as a driver of the costs: https://www.aei.org/research-products/report/paying-less-for... – which notes that "70 percent of contracts in the BGS data in 2024 were for unique buses".