I don’t see any reason to believe this. If all jobs could be done remotely wages would go down in some areas and up in others. Not sure why you would think wages would go down simply because they could be done remotely.
Because remote work generally increases supply of labor. In the short term the bottleneck is managerial resistance to building a culture of remote work. In the medium term when companies see that groups are successful they will search for talent at the lowest cost, duh! There is no magic that says rich western countries will win that competition. Increased global supply of software engineers and other knowledge workers will generally lower salaries unless there is enough demand to hoover all of them up.
Now the counter is that as far as innovation is concerned competition for the best will go up as companies do rely on less, but higher quality employees to get shit done. Those employees do generally (at least for now) come from rich countries, but that too will change. It will change because high quality people will realize they no longer have to emigrate for opportunity.
Josh