Seriously, you dug up something from 3 years ago??
But for the sake of argument, let's have a look at it. Renault built their engine in the expectation it would always run at a certain rpm tom provide exhaust gasses to seal the diffuser. The rules didn't forbid that at the time. What you do, if your engine runs a certain rpm is, that you minimize moveable parts, for instance the flywheel. Also you'll construct oild distribution in a way that is just fine, but depends on a certain level of average rpm, even under breaking. If someone then comes along and says you have to drop rpm (under breaking, which can be a significant part of the lap on some tracks) your engine won't be sufficiently supplied with oil anymore and/or just die because of the minimalistic flywheel. So in essence there certainly were reliability aspects. Now, don't get me wrong, Renault would've been idiots if they didn't sneak in a few upgrades while they were at it, but some reliability issues must have existed, else Ferrari and Merc would have protested the raw crap out of it.