I'm going to go out on a limb and assume that paying someone $200 for a scan is cheaper than creating a person from nothing, and that's the only reason they want it.

Extras are part of the union (SGA-AFTRA). This is why SGA is striking (well one major reason). This is why all major statements from SGA have been that they are starting with extras but will continue on to marginalize and exploit others in the union. Because that’s what capitalism does. It is how it functions if left unchecked.

The unions know that do-nothing parasites that own the studios and other businesses want to get labor cost down to essentially nothing. And they will do everything possible to get it there including openly stating they have more money than god and will simply wait out every single writer and actor until they go bankrupt on strike.

Maybe it’s not so much about the technical part, but more on the legal part? Sure, they can use generative tech to do this and continue to improve upon it, but they don’t have permissions yet and this proposal is just to cover their bases. Hopefully SAG can shut it down completely, as one can presume that this looks like a “door-in-the-face” technique, and the industry will keep tuning the proposal until some actors give in and have big enough checks, which could then cascade to affect the whole industry.

You're right, there's no reason they can't just make a fully artificial human likeness that doesn't require anyone to sign over rights. That only leaves one other rational for this, which is that they want to trick desperate actors into handing over their likeness so if they get famous in the future they can control them.