Pretty much spot on blah... If I may expand a bit more...In your list - before a platter swap is a head swap. platter swaps are really only used in the event of motor failure or spindle seizure, when the platters physically can't spin. If the issue is a head failure or preamp failure, much easier and safer for the data to swap the headstack rather than move the platters. Even with a spindle failure, there are tools that you can torque the platters to try to get them to spin up again long enough to recover
The reason being, that particularly in multi platter drives ( where there are 2,3,4, or in some scsi drive up to 10 platters ) the platters must be moved as a unit and cannot be permitted to rotate even a micron, if that happens data alignment and timing go out the window. Add to that the fact that manufacturers have been adding baffles between the platters that are secured to the frame of the drive, which have pretty much made the previous platter tools useless, and platter swaps are the last thing even pros want to try.
Upon re-reading the OPS post, he may be referring to the infamous 'direct read' of the platters. While it is possible to extract data reading individual bits on a spin stand, assembling it into useable data becomes another thing entirely.
The HD controls how data is actually written to the platters - what the mapping of physical sectors is to Logical blocks. that mapping algorithm is part of the drives firmware structure. So even tho you can read individual bits and bytes directly from a platter with the proper gear - it is
a) not cheap LOL
b) unless you have a major reason to try it - not likely to yield reliable results in an acceptable time period.