No. Assuming it's using steam generators like most powerplants (gas, nuclear, and coal), then the only heat released to the atmosphere would be the inevitable entropic losses. This is the same amount of heat lost by nuclear powerplants (although you could argue nuke plants release decay heat that fusion plants wouldn't but that's negligible). Gas and coal plants release that heat as well, but then also release greenhouse gases that heat things up further
The author wasn’t asking about production entropic losses, but whether using massive amount of energy will heat up the planet, and it definitely will. This is why it’s a technosignature. Heat dissipation is the ultimate limit on growth on a planet, but we’re talking about trillions of people living in luxury.