It didn't surprise me that he missed it, let's put it that way.
There's another problem with your stats, which is they don't take into account shots on or off target. Your numbers are basically all shots in total, whether on or off target.
On that same website, you can go Detailed>Sub-category: Accuracy, and see stats for on and off target.
At Villa (I can't be arsed factoring in his Bristol City stats, and you can't just add them together as the whoscored site does), Kodjia had these stats (if we use your back-calculation method, ignore the decimals, this whole approach is a bit messy):
Off target: 38.4 Hit post: 3.2
Blocked: 22.4 On target: 51.2
(And the calculated Total if we add these up is 115.2)
This means we can work out Kodjia's on target ratio (which I assume is on target + blocked shots) = 73.6/115.2 = 63.9% on target, 36.1% off target.
Whereas for Hugill:
Off target: 35.1 Hit post: 0
Blocked: 11.7 On target: 23.4
(And the Total is 70.2)
So Hugill gets 50% of his efforts on target, 50% off target.
Which is why people say (rightly, I think) Hugill is not a clinical finisher.
He shoots (or heads) less often in total, and gets fewer of his efforts on target, compared to Kodjia (and probably a bunch of other strikers in this league). Also he has scored fewer goals, of course.
Using these weird averages and multiplying them up is obviously not very elegant, but the BBC site also has numbers for shots on/off target, and they have Kodjia at 53%, whereas I remember when Hugill used to be on this list, his shots on target ratio was about 40%. So the difference between the players of about 13% is the same at least.
http://www.bbc.co.uk/sport/football/championship/top-scorers