Why isapprox with atol fails? Is it a bug?

a = [
  -50.04195177226517, -1.0188363863282068, 1.9430393238222883, -0.35084921747818826,
  -8.294359715394497, 1.2782294524103035, 0.5607096408798733, -1.7215746004289658, 
  3.2231929774225057, -0.10300377501347695
]

b = [-50.042, -1.0188, 1.943, -0.3508, -8.2944, 1.2782, 0.5607, -1.7216, 3.2232, -0.103]

isapprox(a, b; atol=1e-4)             # => false

isapprox(a[1:10], b[1:10]; atol=1e-4) # => false
isapprox(a[1:5], b[1:5]; atol=1e-4)   # => true
isapprox(a[6:10], b[6:10]; atol=1e-4) # => true

maximum(abs.(a-b)) # => 4.921747818825706e-5