Yes, that is because of TAE's back end is steam turbine + generator + condenser heat to electric conversion, but for a retrofit fossil plant that is a sunk cost. OTH, Helion avoids the retrofit restriction with direct conversion **using the same hardware used for fusion,** a massive advantage for new installations. TAE will need to **eventually** go for direct conversion.their (TAE) power plants will be significantly larger (in terms of area) than Helion's.
Zap made a breakthrough with a liquid metal electrode which I thought (the electrode) was going to be their major issue. Zap seems to have achieved a good model for their approach based on published papers, so it may be just a matter of time to get high enough electrode current & electronics. Maybe someone has better insight on what the issue is if that is not the delay.