You can certainly make a "scrappy" OBW, with every block being a different fabric if you want to,just every blade of a given block being identical.
The "one block" refers to the hexagon, not the fabric, because *even in an "all one fabric" OBW*, every block looks different from the other.
So how different is different?
It's a matter of degree.
Maybe you will start a whole new fad!!
Go for it.
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