All this is exactly why the two switch circuit is far superior.
All that horrendous 15W (1.5%) power loss is returned to the dc input bus so there is no voltage spike on the drains.
And as the flyback transformer will have an appreciable step down ratio (for battery charging) although the secondary peak current will be high, its nothing some appropriate shottky diodes cannot handle.
I do agree though, that generally very high power DCM flybacks are not practical, but in this case a combination of factors make it quite workable.
I have been working on a fairly novel 1.5 Kw 20Khz buck boost circuit, still in prototype form,
180 volt input, +/- 220 volt output rails, only a single mosfet and over 99% efficiency.
The thing runs barely warm flat out.
It works so well because the voltages are high, the currents low, and the drain voltage of the one solitary mosfet is very solidly clamped.
There is no snubbing at all.
Input is straight from solar panels, it provides +/- 220v regulated dc output rails.