Are all tactical flashlights considered weapon lights?
Any flashlight that fits our ALG-00 and ALG-01 could be considered a "weapon light." There is not an official designation of what defines a "weapon light" but if it fits in either of those weapon mounts it could be mounted on any rifle that features a picatinny rail.
Many lights that have tail cap switches will also be compatible with the AER-01, ARE-02, and ARE-03 remote pressure switches. This would allow an even better option as a weapon light as it would allow for remote operation of the flashlight without having to reach forward to interact with the flashlight itself.