Double iszero seems like an identity on rayDiv?

[Paladin - Team Account]

aave-v3-core/contracts/protocol/libraries/math/WadRayMath.sol

Line 86 in 27a6d5c

 if or(iszero(b), iszero(iszero(gt(a, div(sub(not(0), div(b, 2)), RAY))))) { 

Hey all, diving into some of these libs for a client. Why is a double iszero done here? Seems like its kinda an identity function if the input is already 0 or 1?

Cheers,
Marco