That’s pretty much the same as what everyone uses. Technology has improved the steps along the way but the basics are the same. The current advent of 3D printing has allowed even better results in small lot special props like rc boat props.
Yup, I'm surprised they attach the blades rather than casting the wax as a whole, must still be cheaper that way. Cheaper than 3D printing the wax too I'd bet...
That’s the way Tom Prezenka (Octura) did his first plug, made individual blades on a Deckel pantograph and wax welded them to the hub then investment cast that and used that one as the model to build the molds to shoot the production waxes to be cast for sale.