Yes workers are exploited, but it's also harder to create value when you insist on capturing it.
This is arguable a big idea of free software: trying to jealously hoard the value for ideas that are naturally freely copied and shared is just plain inefficient.
So yes, in this case it would be nice if these interns got a big pay out, but if they did, then the megacorps wouldn't bother using Rust because they plan is already to just outbid all the non-monopolists for workers rather than actually be productive with their workforce. And C++ and whatever else are already free, so Rust has to complete with those.
The only way to make things more fair is just give up on meritocratic value capture, and just do a big tax and big UBI, so just as free software is free to use by all, some of the value created in the use of free software is also freely shared by all.