Not changing orientation of drives after formatting is an old fable that dates back to really early hard drives. It's only something I've heard in relation to VERY early disks (read early to mid 80s) with inaccurately actuated heads and old fashioned bearings. If you turned the drive on it's side the 'slack' was in a different direction and the head read off the edge of each block slightly which could lead to data problems. It's never been something I've ever heard of in anything remotely modern though. as II2II says the accuracy and power of the actuators in modern drives are such that it makes very little odds.
I've only ever had issues with ex-server SCSI drives being used laid flat after being one edge in an array because the bearings in the spindle were shot out and the change of orientation caused the spindle to jam up or drag because of the uneven wear. That's not a formatting issue though and it's exceptional because of the wear circumstances. It doesn't happen (at least not to my knowledge) in modern drives because they all use fluid dynamic bearings, which can cope with extended operation, change of orientation, shock and temperature fluctuation much better.
I believe the recommendation hung around in hard drive documentation for many years after it stopped being an issue however.