Yup, that's the way it works.

It reverses the bits by rotating them into a 0'd variable.

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If you want to preserve the upper 4 bits, you can OR them back in.

B0 = (%10101100 & $F0) | (%10101100 REV 4)

--- Same thing with the value in a variable ---
B1 = %10101100
B0 = (B1 & $F0) | (B1 REV 4)

result = 10100011
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