Your first expression whas of this kind:

result = cond do
  condition -> true
  not condition -> false
end

Which in its nature is very similar

result = if condition, do: true, else: false

Which can always be simplified to

result = condition

The second one is a bit different, but usually, whenever you have a case matching on true/false only, you usually can just replace it by an if, there might be cases where you want to explicitely true/false rather than truthy/falsey checks, then of course you need the case.

And to be honest, about any 2-clause-case that matches on an exact value rather than binding names, while the other arm uses _ can be rewritten into an if by just using Kernel.===/2 or Kernel.==/2, depending on the semantics you need.