It is probably better for Formula 1 if they are open to giving Renault some leeway. A lot has been made of the new engine regulations, and for Renault to have completely screwed things up the way they have is a bit of a disaster because it means that over a third of the grid is under-powered and uncompetitive.
The worst-case scenario suggests that Renault will not be able to fully resolve their issues for twenty weeks, or until the British Grand Prix. That might be exaggerated, but it's clear that the problems will be fixed later, rather than sooner. Such concessions would allow Renault to fix the problem faster, but the Mercedes and Ferrari teams will still carry a massive advantage into the opening races of the season.
If they do not allow the scope for further development, they could also raise the ire of certain teams, namely Red Bull (and Toro Rosso, who will do whatever Red Bull do). Remember Mercedes' double-DRS? Christian Horner fought very hard to try and get the FIA to ban it, or force Mercedes to give up the system's secrets. The last thing Mercedes and Ferrari need is for Horner to try and hamstring them while they are still figuring everything out. There are still questions about Ferrari's turbo shield, and McLaren's rear suspension is highly interpretative of the rules. Horner could - and let's be honest, will - make a fuss over it to try and disrupt those teams. He would do it even if Renault's engine was the best on the grid, and he would pretend it was in the interests of the sport.