Coalescing to zero in arg preprocessor inconsistent between Float and Decimal

Why are these different? Both with and without NIF, dealing with null argument should be happening. Is there an optimization happening in NIF that isn't happening for Decimal?

> Option( Options.NumberIsFloat, false )
false

> IR(DateTime(1,1,2,1,1,1))
DateTime:d(Coalesce:n(Float:n(1:w), 0:n), Coalesce:n(Float:n(1:w), 0:n), Coalesce:n(Float:n(2:w), 0:n), Coalesce:n(Float:n(1:w), 0:n), Coalesce:n(Float:n(1:w), 0:n), Coalesce:n(Float:n(1:w), 0:n))

> Option( Options.NumberIsFloat, true )
true

> IR(DateTime(1,1,2,1,1,1))
DateTime:d(1:n, 1:n, 2:n, 1:n, 1:n, 1:n)

> IR(DateTime(1,1,2,Blank(),1,1))
DateTime:d(1:n, 1:n, 2:n, Coalesce:n(Blank:N(), 0:n), 1:n, 1:n)