Why is this an issue?

Two methods having the same implementation are suspicious. It might be that something else was intended. Or the duplication is intentional, which becomes a maintenance burden.

class Circle
  def initialize(radius)
    @radius = radius
  end

  def width=(size)
    @radius = size / 2
    update_shape()
  end

  def height=(size) # Noncompliant: duplicates width
    @radius = size / 2
    update_shape()
  end

  def updateShape()
    ...
  end
end

If the identical logic is intentional, the code should be refactored to avoid duplication. For example, by having both methods call the same method or by having one implementation invoke the other.

class Circle
  def initialize(radius)
    @radius = radius
  end

  def width=(width)
    self.diameter = width
  end

  def height=(height)
    self.diameter = height
  end

  def diameter=(diameter)  # Implementation is shared
    @radius = diameter / 2
    update_shape()
  end

  def update_shape()
    # ...
  end
end

Exceptions

Methods with fewer than 2 statements are ignored.