I would not think so. Damping factor affects mainly smoothness of frequency response, because it is inversely related to output impedance of the amp. A high DF gives smoother frequency response on a speaker whose impedance varies with frequency (most of them).
DF is frequency dependent and conventionally measured at 1 kHz. Unless you have a graph of DF showing it is 4000 at higher frequencies, it is probably lower there (though maybe not relevant to your question).
I don’t know if this applies to your situation, but sometimes distortion in the high frequencies can masquerade as more extension. If the Hegel has lower distortion than a previous amp, it could give the impression of less extension. I've not listened to any Hegel amps, so I don't have any insight there.