That they're LED is of little importance. What is of major importance is the way LED replacement bulbs are constructed versus halogen.
Halogen and incandescent bulbs use a tungsten filament as a resistive element which glows very brightly to produce light. Compared with an LED it is extremely small for the luminosity provided, and is capable of producing light in essentially 360 degrees. There are also different ways the filament is oriented in the bulb which places the light in different positions relative to the center of the bulb. Halogen reflectors are engineered very specifically to focus light coming from the bulb in a controlled and predictable manner. If you take a horizontal-filament bulb and place it into a housing intended for a vertical-filament bulb, you will lose effectiveness.
LEDs are directional. The way these replacement bulbs compensate is to use multiples of them arranged radially to produce 360 degrees of light. Absolutely none of them place the same quantity of light in the same location as a tungsten filament, which is why nearly 100% of LED replacement bulbs are non-compliant and illegal for use on most public roads (enforcement however is virtually nil).
If an LED bulb was constructed so as to exactly match the position and luminosity of the tungsten filament it replaces in the halogen bulb, you would see a viable alternative to place into rotators like the ones above. The current technology is probably close but I haven't seen anything suitable for use in a rotator. Given that LED beacons and mini-bars are widely available, cheap, and generally bright and effective, there's little reason not to just replace the entire lamp.