Your second image says to loosen all four hold down screws. Loosening only the two front screws would cause a great deal of stress on the other two screws and on the adjustment screws.
Rather than tracking taper as suggested in the second image, I prefer to look at the ability to cut a flat face. I made the mistake of adjusting the headstock to correct a taper issue when I first had my G0602. As a result, I was cutting a face at an angle. Taper is also affected and usually corrected by shimming the tailstock to remove twist and adjusting the headstock is using two wrongs to make a right.
To check for a flat face, I mount the face plate with a boss mounted on it. The purpose of the boss is to provide a raised surface for sweeping a test indicator across. A carriage bolt works great for this. The face plate is rotated so the boss is forward and the center of the boss is in contact with the test indicator. I place a mark on the boss so I always contact it at the same place. I zero the indicator and lock the carriage. Then I rotate the face plate and advance the cross slide to hit the boss at the same point at the rear of the lathe. The indicator reading should be zero. If it isn't, you will be cutting either a dish or a dome, depending on which direction the indicator has moved.
I adjust my headstock to correct any issues as on my lathe, at least, there is no other way to make this correction. I then check for taper, either using the RDM method or the two collar method and correct any issue by shimming the tailstock.