This isn't a problem. The article says that this is only if you're looking to trade-off performance for less noise:

> In other words, we would only recommend upgrading to the NF-A12x25 G2 if you seek to lower noise levels as much as possible and if you are willing to sacrifice the maximum performance headroom in worst-case scenarios that the G1 HS-PWM fan provides.

That's for switching to the NF-A12x25 G2 fan (from the G1), which has a lower max RPM. The improved side panel appears to be a strict improvement.

It doesn't say that:

> In addition to redesigning and testing the Noctua fan grill, we also evaluated various other scenarios. These included replacing the NF-A12x25 with its G2 variant and incorporating an additional 8cm fan for exhaust purposes.