What is recommended in newer versions is to use a cardboard to cover EITHER one OR the other set of contacts.
I.e. the general idea is to flip a coin, if it comes out head you cover the head contacts and attempt the procedure.
If it comes out cross, you cover the motor contacts and attempt the procedure.
If the procedure doesn't work, you re-do from start, i.e. you power off EVERY device involved, take all the time needed to unscrew/disassemble again the PCB and place the card on the "other" set of contacts.
Unfortunately we have a very small number of people willing to re-brick their HD to see if the "other" procedure works... so we have NOT a reliable database of which of the two set of contacts has given "better" results.
But we have a single positive, documented result (in the mentioned guide):
You might also want to notice how it is perfectly possible to insert the cardboard under the "motor" contacts by unscrewing/loosening one single screw, though it is NOT recommended (but there is no need to completely remove the PCB, at the most you need to loosen another one or two screws), whilst to try inserting the cardboard under the "head" contacts you need to unscrew/losen at least three of them or, more likely, the complete removal of the PCB may be necessary.
Try passing the above over Occam's Razor:
And see which choice is more worth trying as first attempt , then make your choice, but choose wisely...
Seriously, there is no actual way to know this whole topic is permeated by some kind of "magic", we miss too many proper reports and actual knowledge on the way the stoopid hard disk works to be able to suggest one or the other.
The theory is clear: induce an error on the board in order to allow access form the terminal, the original guides, which said to completely remove the PCB and re-mount it whilst powered, obviously created the error by disconnecting BOTH sets of contacts.
Though actually not that difficult, it is potentially very dangerous as a simple slip of the finger or a screw falling may fry the powered-on board, I would estimate that in the hands of an average user doing 15 times the cardboard trick for each set of contacts is roughly as dangerous as doing it once with the removal/re-assembling while-powered-on approach.