The PREVIEW is there to generate a different Preview image, if the pattern/sticker isnt visible by default...
patterned/stickered parts have to be the same origin and orientation as the base part, so it is possible that the pattern/sticker is on the backside of the part.
to be visible in the Preview, the meta tells the preview generator to turn the part first.
Minifig heads are mostly printed on the front, so it doesnt need the command.
but for example, panels or other bricks which can be decorated on different sides.
a minifig head brick will always be decorated on the front, because it can be rotated -> printed side "defines" the front side
for example, this part: https://library.ldraw.org/parts/44196
the base part is with the hinge to the front, so the long side with the sticker is on the back.
the part cant be rotated itself, so the preview wouldnt show the sticker.
Minifig heads should keep the standard view, also to show the stud type and sometimes its also to see if the head has a back print...
patterned/stickered parts have to be the same origin and orientation as the base part, so it is possible that the pattern/sticker is on the backside of the part.
to be visible in the Preview, the meta tells the preview generator to turn the part first.
Minifig heads are mostly printed on the front, so it doesnt need the command.
but for example, panels or other bricks which can be decorated on different sides.
a minifig head brick will always be decorated on the front, because it can be rotated -> printed side "defines" the front side
for example, this part: https://library.ldraw.org/parts/44196
the base part is with the hinge to the front, so the long side with the sticker is on the back.
the part cant be rotated itself, so the preview wouldnt show the sticker.
Minifig heads should keep the standard view, also to show the stud type and sometimes its also to see if the head has a back print...