Unsigned BC6h sampleLower is negative #16

Hello 👋

the example DFD for unsigned BC6h in table 48 (around here, not sure how to link to the actual table) has a sampleLower of 0xBF800000U = -1.0f although it's an unsigned format, and the signed flag is not set in the channel qualifiers.

Is this an error in the table or an intentional choice? dfdutils doesn't make this exception and chooses sampleLower = 0.0f for _UFLOAT Vulkan types, contradicting the example.