I think in a Deutritium-Tritium fusion reaction a lot the energy is in the neutron. And since neutrons are neutral you can't really directly convert that into electrical energy.
Yep, for D-T 80% of the energy is in neutrons. Helion is using D-D/D-He3, and for that it's about 5% in neutrons, and most of the rest in fast-moving charged particles.
So they have a simple way to extract electricity directly. They squeeze the plasma with a magnetic field from a copper coil, then there's an explosion of charged particles, which pushes back against the magnetic field and causes electricity to flow in the coil.
As I said, the combined reaction generates 5% of its energy as neutron radiation. The reason it's only 5% is that D-He3 is a much more energetic reaction.
The main issue with D-He3 is that it's more difficult.
