I never realized drives were open to the atmosphere. Makes sense now that you explain it. I hope the filter keeps out cat and dog hair.
So check this out. The hard drive head has tension that pushes the disk into the platter. When any surface moves it creates it's own "skin" of the "fluid" around it (in this case, air). This is called the Bernoulli effect, read up on Wikipedia if you want to know more. For hard drives, and at standard air you can get a fairly good range that works well when engineered with a proper head. The disk spins and you end up with air that "sticks" to the platters. The head then rides on this platter. Ideally the head would only touch the disk when it is spin down (ever wonder why we don't recommend shutting down servers and such.. this is one such reason). Anyway, if the head gets too close it gets pushed away from the platter and if it gets too far it loses buoyancy and the tension from the mechanical arm pushes the head back within close proximity. For many disks the cushion of air the disk rides on is about 75 MPH in relation to the stationary head. A "head crash" is when a hard drive has the head physically hit the media while it is rotating. This is obviously very bad. There are lots of variables to deal with however. As atmospheric pressure changes based on your elevation on the earth, solar wind's impacting on the atmosphere, cold and warm fronts, temperature, etc all of these affect how the "skin" of air behaves on your platter. How much, I don't know. But they are definitely there.
Some of the newer (and better IMO) hard drives park the heads completely off the platter on a loss of power and the head won't move onto the platters until the disk spins up. This means that ideally your head will never come in contact with the platter (which can only be good, right?).
So with He you have different resistance, different thermal properties, and different "skin" because of the properties of the fluid. I would presume that He would allow for the head to be closer to the media (both a good and bad thing) and obviously He provides superior cooling (this is probably a good thing). I wouldn't be surprised if He disks were even more susceptible to damage from slight motion while the disk is in motion but provides longer life when installed in a Chassis with all screws installed and tight (notice I didn't say rubber grommets to absorb noise). We've all had that external SATA drive hooked up to our USB port with one of those converters and had to pick up the drive to move it and we'd do it very gently. It's possible that these He drives could be seriously damaged by that kind of thing. I don't know and only time will confirm or deny my guesses.
I do hate the new "shingled magnetic recording" drives though. The technology just scares me.
I do like the idea of HAMR technology, but time will tell how reliable and how dense the technology will go. I tend to look at shingle technology as the current stop-gap because of delays with HAMR technology but the need for bigger disks. I think once HAMR comes out shingle tech will die pretty rapidly.
We may find that the 40C "thumbrule" for keeping drives healthy and happy can be increased to 45C and we may find that we shouldn't let the hard drives cool down to some low temp like 20C. He has the possibility to upend many of the hard drive physics, thumbrules, and such that we have previously taken for granted based on decades of knowledge. These are definitely interesting times for the hard drive market.
Time will tell though!