Yes this is discontinuous conduction mode.
It is interesting that the current in the coil at some point begins to flow back through the MOSFET's diode.
Let us start to track. Please see the Purple-Source voltage trace as well as White-coil current curve that I tried to draw.
Points 1-2: MOSFET opened, flywheel diode closed, the current rises.
Point 2: Mosfet starts to close, the coil current can't stop and decrease voltage at Sourse until flywheel diode opens at point 3.
3-4: coil passes the energy to the load and the current falls until zero - point 4.
At point 4 we have at left coil side 0V and at right side +30V - current reverses its direction and flows back until bouth coil sides catch up 30V - point 5.
Here the current flow starts to decrease but cann't stop immediately and at point 6 the Source voltage reaches more than 40 V and opens back MOSFET diode.
Points 6-7: the current flows back via MOSFET.
Point 7: MOSFET opens, current changes direction to forward and starts to increase.
You can see that 6-7 is one pixel higher than 7-8 (MOSFET diode drop voltage).
PS
It would be interesting to intall the current sense resistor and get the current trace.