DHS uses Aramid-Carbon on the HL5 and W968, not ALC. I've written this somewhere else, the composition on those blades isn't exactly the same, there is a fundamental difference between them. The commercial version of the HL5 uses (or used, it appears they may have changed this) what I call Ay-C. This particular type of fabric only has aramid in the vertical direction and carbon in the horizontal direction. The higher flexibility of aramid is responsible for the lower frequency reading. The W968 uses a plain A-C fabric, with an equal ratio of fibers in both directions. This gives it a bit more stiffness, but also more softness, and the frequency is usually in the lower 1300s Hz.
The new generation of W968 has a higher frequency, closer to 1400 Hz, which tells me they messed with the stiffness somehow. This can be done in a number of ways, but the most obvious one is the lamination process of the A-C layer. This is also something I often experiment with. I also see a small, but relevant difference in the plies, so it can be one of the two, or both.