You can design a QR flyback to be clamp-less - usually a bigger cap across the FET ( or Tx, or both ) - this guarantees a ring down to gnd - which gives losses less turn on - fast turn off gate drive gives very low loss turn off ( as the Vds rises more slowly ) - the slower rate of rise of volts across the mosfet ( and Tx ) helps the o/p diode turn on in the face of some leakage inductance - the turn off ringing overshoot can be quite high though - so 800 - 1kV fets often used - but the RFI is low and the eff is high - and less snubbing needed on the o/p diode - so win, win, win
The fet does take a bit of a hit at 1st turn on though - but usually larger fets are used anyway in flybacks - so not too much of an issue ....