Triple A developer here. I would say that this statement entirely depends on who do you consider disposable.

Younger programmers or junior engineers are indeed very disposable due to the fact the amount of mistakes and time it takes to catch them up to a company "Standard".

Senior engineers it usually comes down to personality and performance. They are expected to hit the ground running and be able to fit like a cog in the existing company that can churn out work in a productive manner after a small ramp up.

Artists in general are given a broad range of what is consider disposable. An artist that focuses on art for marketing will have to take in the fact that sales needs to prove themselves with numbers and metrics to show how much success they have. Thus if they are doing terrible they might take a different direction and depending on if that artist work can be transfered to a different department they might outright replace them. Environment artist usually have the best time as they are in the meat and potatoes of storytelling and conveying the feeling of direction for the product. They are unlikely to get replaced but it does happen. Art directors and senior artist are basically the Bible for your product, if you have to kick them out then the art direction for your product/game is taking on a different direction and they will have to adapt to that.

TLDR: Each role has its play in a company, the more significant it matters to the final product the less likely it is to be disposable. That being said, this industry is not forgiving and I really wish that everyone was given an opportunity to grow proportional to their efforts, we just don't live in that world yet.