I think it's a silly idea and not very well-thought out.
Firstly, it's blatantly stupid that they post such an announcement without any elaboration or link to information. You have to search for it yourself somewhere on the forum (thanks
@SavreticD ).
It could lead to interesting (not in the positive way) schedule strategies. You would want to let low iRating drivers drive in the early-mid part of the race. That way if they crash or get crashed out the team's iRating is as low as it can be and only the drivers who have driven will lose iRating, and since their iRating would be less than or equal to the SoF they wouldn't lose too much.
Alternatively, if you let the high iRating guys drive first and there is a crash towards the end, the team's iRating will be high and the high iRating guys will lose a lot even though they may not have contributed at all to the crash. Meanwhile, it could be a low iRating driver on his 1st/2nd stint who totals the car and he would barely lose any iRating.
And what about solo drivers? Obviously they would not gain or lose iRating because they get DQed but teams will claim these drivers had an effect on their race. "We would have gotten another position but I was held up by a solo driver who has nothing to lose."
@Deb I think it mostly depends on your expected finishing position in the race. If you are in a 3000 SoF split and early in the race think you won't finish well as a team then you could do damage control and let the lower iRating drivers do most of the driving. If early on you expect to finish well you have to decide between 1) using some high iRating drivers, possibly ensuring a good position and reasonable iRating gains for all drivers, or 2) using low-medium iRating drivers, possibly losing a few positions but also lowering the team's iRating to gain reasonable iRating for all. There is probably a fragile equilibrium there where both choices net the same exact outcome.
We might be able to calculate what the most profitable strategy is. For example, say in situation 1 driver A with 4000 iRating drives 70% of the race and driver B of 2000 iRating drives 30% of the race. Then the team's iRating is: 0.7 * 4000 + 0.3 + 2000 = 3400. Say they finish such that they gain 50 iRating. Driver A gets 35, driver B gets 15.
If we turn that around, driver A drives 30% and driver B drives 70% the team iRating becomes: 0.3 * 4000 + 0.7 * 2000 = 2600. To get the same iRating gains (driver A gets 15, driver B gets 35), the position in the race must be such that they still get 50 iRating from their finishing positions @ 2600 team-iRating. If this is how it turns out on average is really difficult to say because it depends on the accuracy of each of the drivers' personal iRating, the iRating distribution of the opponent teams in the race, the number of cars and non-starters etc.
@Brainling Yes, maybe. Another reason I can think of is making their upcoming WEC-like endurance series more popular/prestigious.