Yup. But the PWM is very high frequency and isn't detectable to the naked eye.
Compared to current control, High frequency PWM has the following differences:
* Better tint with less tint shift. Many LEDs tend to produce better tints when run at full power. With current control at low power they sometimes start to look green. Lights that use PWM maintain the same tint at all brightness settings and even at lower power settings the tint still looks good.
* The D4 has a single 7135 regulator chip for low modes and a FET for higher modes. As such, there might be tint shift when switching from the 7135 to the FET (happens around 130-160 lumens depending on LED choice). Below that setting all outputs will have one tint. Above that setting all outputs a slightly different tint.
* LEDs are more efficient when run at low power. Lights with current-control drivers are more efficient when run at less than maximum power. A light with a current-control driver such as a Zebralight, should have a longer runtime at the same lumens on pretty much every setting except the point where the 7135 chip is running at max (130-160 lumens). When run at max power, LED has the same efficiency regardless of which driver is used. However, because the D4 pulls far more amps than any Zebralight, it will have lower runtimes.