No, he is not lying. I thought about this after you posted that and I think I know what he is doing.
Surprisingly, both are true. What I said above, if you install two inlet cams based on their original orientation, the bike won't run at all is true, because the exhaust valves will not open at the right timing. But, it's a 180 deg parallel twin, so the cams are really the same overall shape. That's why this works on this particular engine configuration. What you have to do is install the cam that goes over the exhaust valves in the correct timing position, so that it opens the valves at the correct time, ignoring the factory markings.
You want to make sure you set up the timing correctly, because you could damage the valves/pistons if they are off.
The Ninja 650 cams are taller and have a longer duration, so swapping the cams gives you better breathing at the high end. On both the Versys and Ninja, the intake cam is setup to have a longer duration than the exhaust. So when using that two intake cam solution, at high RPM, this gives you better scavenging and better high end output. But, at low RPM this results in lower cylinder pressure and lower output and torque. Seems like a good solution for someone who is racing and is interested in the top end power output more than everyday drive-ability and performance at road speed conditions.