There is no constraint that prevents professors-researchers from paying more for students and post-doctoral researchers. In fact, in most universities, professors can give them financial support at their discretion. There's a lot of talk about federal granting council awards, but faculty who receive grants also give money.
If these grants aren't indexed, faculty will have access to the same amount of grant money, but will have difficulty keeping pace with income indexing for students. Council grant programs haven't been indexed either, and haven't been for a long time. A grant that was worth $1 million in 2000 would be worth much more today. The problem is that today, $1 million is still being paid out. So if the professor decides to give a lot more money to his students, he may compromise some of his research activities or he may have to make choices about research programming.
I think there's a link: If the awards are indexed, then the research grants to the faculty in our universities should be indexed as well.