Apparently, it actually has to do with Vulkan support, which makes this more of a GPU issue. Vulkan released in 2016, and while it was backported to many earlier GPUs at the time, this wasn't universally successful, hence the 10 year disclaimer. Still, building on Vulkan is a good move, so this seems entirely reasonable to me.

Even if all that wasn't the case though, "[older hardware support] wouldn't have been expensive at all" is a baseless claim.