Over the past 35 years of riding I have had more helmets then I can remember. I have 3 in the rotation now and two more in the basement. Never had this issue with a short chin strap. I wish this one had a strap that was too long were you had to cut away the extra. just giving my review as a actual owner of this. The one at the vendor tent fit perfect the one I got online didn't. Same size. Take it for what it is.
Well, I might offer that your experience shows a lack of quality control at the manufacture regarding strap length, but this isn't reflected by the reviews I've read. Amazon reviews gives this a 4.6 out of 5 star user review rating (691 ratings last count) and I scanned a few dozen of the reviews with none mentioning a too short strap.
My strap had enough length that I cut 3" off it because I didn't like the look of the extra length hanging. Then, after you mentioned the teeth of the latch only engaging on the last few 'teeth' I realized mine was doing the same so I adjusted my strap looser by about 1/2" and my 'teeth' fully engaged.