I've tried on a couple of the POC 'road' helmets, including the Spin. While they seem -really- high quality, they look and feel very bulky/boxy. I don't think it is a big surprise you don't see a whole lot of triathletes racing in it.
That said, their real aero helmet, the POC Cerebel, different story, great helmet if it fits well.

For when you're on your road bike, not racing Tri's/TT's right? Another happy Specialized Evade II owner here.

Interesting! Is it that much bulkier than something like the Bontrager Ballista MIPS, though? Also, does it matter how big/bulky it is if it tests well and weighs the same?

I honestly don't know how it compares in terms of weight or actual aero, I just know that when I had it on and looked in the mirror, it looked and felt bulky.

Here is a sample pic from google, can kind of see what I mean from the pic from above? Might just be me, but looks wide...

https://www.farfetch.com/...t-item-13901746.aspx

HJC Furion. Wind tunnel tested and light (190g), but not legal for USAT unless you have a pro card.

+1
By far the most comfy helmet I've had. Light too.