PWM reduces the current

Can PWM safely be viewed as an effective voltage reduction?

PWM alone does not effectively lower the voltage for this purpose. The problem is that PWM creates a voltage that is a function of time. It has MANY DIFFERENT VALUES, no limited range (as an LED can tolerate). What puts an LED at risk can be an average, rms, peak V, or peak current (which is a non-linear function of the applied voltage).

Assuming 90 lumens / watt and a "100W equivalent" lamp means 900 lumens, you want about 10W into your roughly 30V LED load. 330 mA DC is the desired current.

A linear regulator (LM317) could work; It only has to be designed for the difference between the input and output voltages (44 V - 30 V = 14 V) and not for the 44 V. The most effective way to regulate the current is to use a current sensing resistor like this:

simulate this circuit - scheme created with CircuitLab

The resistor and regulator will get warm, so you'll need a heat sink.

To improve energy efficiency, PWM, followed by a filter inductance and a catch diode, is called a "buck" voltage dropper. It filters, but does not regulate (without any feedback), so that the battery condition and the ambient temperature influence the current. Buck regulators are available that regulate, remove almost no heat, and improve battery life. Many suitable modules are based on LM2596.