Oh sweet Jezus not this argument again. We just went through it again on ADV Rider.
I know it's tempting to mislabel a motorcycle engine (mostly just twins) by the orientation of the cylinders, but like every automotive manufacturer I'm going with crankshaft/output shaft orientation.
If the crank/output is inline with the chassis it's longitudinal.
If it the crank/output is perpendicular to the chassis, it's across/transverse.
Would you call a modern JAPanInc. or British L3/L4 engine or hell a parallel twin longitudinal?!?
Hell I didn't watch the whole video but even the video called one of them longitudinal in the first few bikes.