I don't doubt that is true, but we haven't been talking about feeding power supplies or (external) 'LED drivers' with a DC supply. Rather, we have been talking about using the ELV "DC" output of such a PSU/'driver' to feed an LED lamp which is specified as working with either AC or DC.
There are very probably some ELV LED lamps whose internal current control is such as you describe, but they would hopefully not claim to work with DC (because they probably wouldn't!). Having said that, as you've pointed out, the "DC" output of some of these things actually consists of high frequency pulses, so it might get significantly through a capacitor (particularly if its value was designed for 50 Hz) within the lamp.
Kind Regards, John
