I think you are mixing several topics.
- An induction heater may use a parallel capacitor to compensate the low coil inductance (air coil or coil with large air gap)
- To convert the output switcher square wave to sine, you need a series inductor, implemented either as separate inductor or a by the transformer leakage inductance, and a series capacitor to put it in resonance. The function can be achieved by C1 || C4 in your schematic, C6 isn't needed.
- Finally, you want a certain amount of inductive load to allow zero voltage switching. Respectively, a parallel LC circuit would be tuned to a resonance above the switching frequency.