The Ruger MK series field strip is certainly not a myth. This didn't just start ... it has been a difficult task since the first Ruger Standard was shipped in 1949. When I owned my gun shop, at least a couple guys would come in every month with a disassembled MK Series in a bag. After I showed them how to reassemble, they usually caught on but you could plan on seeing some of the customers 2 or 3 more times before they either learned the tricks or got rid of their pistol. I'll bet I trained a thousand people in the 31 years I had my shop.
Most people never bother learning how a MK series pistol works. The field strip secret lies in the position of the hammer and hammer strut. To compound the issue, Ruger installs a cross pin that couldn't possibly be in a worse position to hang up the hammer strut.
The confusion starts when you have to dry fire to release the main spring tension on the hammer strut before you can unlatch the mainspring housing. Of course that isn't possible with a MK III unless you have an empty magazine in place ... thanks to the magazine disconnect. After you've had the receiver all apart, the hammer must be fully to the rear to put the bolt back in and fully forward to reassemble the mainspring housing.
When you get ready to put the mainspring housing in place, you must hold the trigger back and use a pencil or other tool to push the hammer forward. Again with a MK III, the trigger doesn't release the hammer without a magazine in place. When you seat the mainspring housing, the hammer strut must be placed in the "pocket" for the mainspring (AKA hammer spring). Then you can close the "knife blade" and latch it shut. The first thing you always do is try to operate the bolt by pulling back on the bolt ears. If the hammer strut missed the pocket, the bolt won't pull back. Release the knife blade latch and try again. Before the hammer strut will align, the muzzle must be pointed up at a 60 degree angle. Once you get the angle of the dangle right, it's a piece of cake. The Ruger manual has a decent procedure but it doesn't explain why you must hold the gun in some bizarre manner so most people end up thinking it is some cult worship and do it wrong.
I'm with Wuchak. The speed strip kit is just another gimmick to relieve you of money. Use the manual or the video on Ruger's web site and learn how to disassemble / reassemble then spend the money on ammo.
BTW, all this and much more are included in the free MK Series IBOK. If you have 10 or more posts, look for it in the NCO Club Library.