Tate Martell just granted immediate eligibility at Miami-Fla. No evidence I'm aware of, but I'd submit that the P5 schools are more likely to benefit from immediate eligibility than others.
It might, yet we've seen transfers in both directions. We've seen players who were backups at P5 schools transfer to the MAC, and we've seen players from the MAC transfer up to P5. It's not all that clear, yet, that P5 will benefit at the expense of G5, or vice versa.
I'd say that the strength and desirability of academic programs will also play a part. In most cases, the player transferring may be looking for a route to the NFL, but in other cases they may realize that the NFL may not be their future, so they may be using sports to get an education that they think will be beneficial to their future. Some of the graduate transfers that Ohio has seen were clearly looking to get into the Sports Management program.
We'll just have to wait and see how it works out.