I have bought VG books listed as VF but purposely only bid & paid VG prices for them because the photos clearly showed them to be lower grade. Maybe I'm being cynical here but in the UK it seems it's perfectly OK to list low grade books and describe them as high grade, using the tired old trope that 'grading is subjective' so one man's VG really is another man's (the seller's) VF.
Fourth item you mention, tricking CGC to award higher grade than book warrants, is fraud, but you try proving it. The others are creative marketing.