During my entire career in helicopter aviation I was always lucky to get to fly with some very experienced flight instructors. When I went for my CFI I received some special training on full touchdown autos. My flight instructor sat down with me and asked me to explain how I would do an auto and why I would do it that way. When I was finished he explained his point of view. And yes, he was right. No matter what helicopter you are flying in, aft cyclic first is absolutely essential. At this point we were not even talking about the aerodynamical reasons but here is the scenario according to Murphy's law:
When will the engine failure take place? When you are not prepared for it.
So, assuming you are out on a long x-country, you don't know how to sit any longer and your butt is aching - cause despite the fact we are flying Volkswagens for the price of a Rolls-Royce the manufacturers still haven't figured out how to produce seats that justify that kind of price - you finally come up with the idea to stretch your legs and place them on top of the pedals. Than you need to change the frequency on your radio. So you reach down with your left hand and.... the only thing which is still under control is the cyclic.
The engine quits and if you don't do anything about it it's not only the RPM which will drop but also the nose of the helicopter resulting in a further drop of RPM. If in this situation ONLY the collective was lowered the nose would drop even more resulting in a less effective increase of RPM caused by the intended lowering of the collective.
Consequently, the only way to recover from this situation is to apply aft cyclic, sufficient to keep the nose from dropping and sufficient to keep your RPM from decaying. This will give you the extra amount of time to get your hand back on the collective in order to lower it.
From the aerodynamical point of view you have to keep in mind that everytime you lower that collective the nose of the helicopter wants to tilt forward initially resulting in a decrease of RPM if no further action (e.g. aft cyclic) was taken.