Head parking is a good thing, since it lowers idle power drain and protects against shocks much better during the period the head is parked. The problem is that WD decided to be very aggressive with head parking, letting it happen every 7 seconds.
Instead of disabling head parking completely, you can opt to set it at a much higher value like 120 seconds. That should prevent continuous parking when the drive is regularly used, but still allows head parking during those periods where the drive is not used, but still spinned up and ready to process I/O in no-time.
Leaving the head-parking at default 7 seconds results in very high Load Cycle Counts (LCC) - which can be displayed with a SMART reader like smartmontools (smartctl -A /dev/...). For most consumer disks the rated cycle counts is between 100.000 and 300.000 but I've seen disks with a year spinning time to be as high as 400.000. This could cause the disks to fail prematurely due to excessive head parking, wearing out the mechanical components to a degree that exceeds the cycle count it was designed for.
There is no reason to use special "RAID certified" drives for a Linux software RAID array, though. Those drives, such as the Western Digital RE series, has a proprietary TLER feature which is needed with Windows FakeRAID and regular Hardware RAID, since those RAID engines typically disconnect a disk that is performing recovery. Linux and other non-Windows software RAID is not affected by this, and as such have no need for TLER/CCTL/ERC feature. Activating TLER on a Linux software RAID might even be dangerous, because it shortens the time the harddrive spends on error recovery. If your array is degraded and one disk has a weak sector, you would want to let the drive spend as much time as it needs to try to recover that sector, instead of being returned an I/O error which is what happens with TLER and its equivalents.