Thanks for the explanation.If you have the same voltage, dropping impedance by half should double power.
So in this case the amp with 48 volts had 69 watts at 8 ohms and 146 with 4 ohms. You really wouldn't have expected more than 138 watts. So a bit odd, but not current limited.
With 32 volts the results were 40 watts for 8 ohm and 70 watts for 4 ohm. Without current limiting you would have expected 80 watts into 4 ohms. So mildly hitting the current limits of this amp's output capability.