The recipe for turning "Thallasium Ore" into "Thallasium Ingot" is 10 seconds in BOTH the Furnace and Blast Furnace, meaning that if you smelt it in the blast furnace, you'll end up spending 2 fuel instead of one.

Because of this I am to assume the blast furnace recipe was incorrectly given a recipe time of 200 ticks, and not 100.

Version; 1.16.4-1.6.0