The following line:

(1 & num) == 1

does raise the following error with Rubocop:

Style/BitwisePredicate: Replace with 1.allbits?(num) for comparison with bit flags.
  (1 & num) == 1
  ^^^^^^^^^^^^^^

But these are not the same statements. It's easiest to see with num = 3:

irb(main):001> (1 & 3) == 1
=> true
irb(main):002> 1.allbits?(3)
=> false

It looks like the actual fix in this case is the other way around:

irb(main):003> 3.allbits?(1)
=> true

If the original source is (num & 1) == 1, the suggested fix is num.allbits?(1), which is actually correct.

The matcher is defined as follows:

# @!method allbits?(node)
def_node_matcher :allbits?, <<~PATTERN
  {
    (send (begin (send _ :& _flags)) :== _flags)
    (send (begin (send _flags :& _)) :== _flags)
  }
PATTERN

And the suggestion as:

bit_operation = node.receiver.children.first
lhs, _operator, rhs = *bit_operation
preferred = "#{lhs.source}.#{preferred_method}(#{rhs.source})"

So this probably needs to flip the lhs and rhs in the output in case the _flags matches the lhs.

RuboCop version

1.79.2 (using Parser 3.3.9.0, rubocop-ast 1.46.0, analyzing as Ruby 2.7, running on ruby 3.3.7) [x86_64-linux-gnu]

(Seen on older versions too)