Too many vowels. All that is going to do is confirm that, yes indeed, the word has vowels. The thing is that all words have vowels so if you pick a starting word that only has a couple of vowels, even if none of them show up in the puzzle its telling you that the other vowels do show up. Normally if you can figure out the consonants quickly the vowels just fall in place.
I would disagree in the sense that either method has its positives and negatives. As you said, it is guaranteed that at least one of those six vowels is in the word - in the vowel heavy approach, after the second guess I know all the vowels. Their
arrangement gives clues as well - pointing to or eliminating certain letters, narrowing down your guesses quickly.
Of course you can get something like _ATCH on your second guess, and not get it right without doing a "consonant dump" word because BCHLMPW all work.
Looking at the analytics you posted, a lot of people go with the vowel-heavy approach to start. Be interesting if you could learn which approach is more successful. Either way you,re playing the odds depending on the word.