I figure it is unlikely that there have been any formal peer-reviewed, rigorously controlled and blinded studies on this important issue, so I went to see what the manufacturers recommend.
I randomly sampled some manufacturers (with perhaps some skew towards major manufacturers having manuals available online), and chose one manual each.
Of the five I sampled (e.g. , ), four had lots of advice, such as turning pockets inside out and being careful of zippers, but no mention of snapping.
One came close when it suggested:
To achieve a better drying result, loosen up heavy loads before
loading it into the dryer
I assume that is referring to large sheets and blankets and the like.
In conclusion, any effect of snapping out the clothes is too small for the manufacturers to recommend in manuals that are otherwise filled with minutiae on improving the dryers' effectiveness.