The Vf is what drives the led to allow more amps to flow through it. You can drive leds with constant current unregulated voltage or constant voltage and unregulated current. For the latter as the led heats up it will draw more and more current until it destroys itself. Therefore the safer way to drive leds is to set a current limit and allow the voltage to be whatever it will be. For instance I have a diy 100w light that is really well cooled with a big fan and heat sink. This setup doesn’t need to be current driven I could set the Vf and forget about it. The driver is capable of delivering many more amps than the LED is using but the led will only use more amps if I increase the Vf (voltage differential across the led). Hope this isn’t confusing and somewhat helpful!
Oh and I think a lot of people are confused about how LEDs and current actually works. When you look at some datasheets for LEDs you will see that the Vf is plotted along the x axis aka the independent variable and the forward current is plotted on the y axis aka the dependent variable. This is because the forward current is dependent on the forward voltage.