I don't know why it was removed, but if you need that to work you can define
function Base.isless(A::AbstractVector, B::AbstractVector)
a, b = length(A), length(B)
a == 0 && return b > 0
for i in 1:min(a,b)
A[i] != B[i] && return A[i] < B[i]
end
return a < b
end
and then your example your work.
