You hit on it - blocking.
Kittle and Duzey were guys that could have been nice targets earlier in their careers but they didn't see the field until the could block consistently well.
I do think Fant will be given the opportunity to learn on the job, to a degree, and perhaps Hockenson will, too. I don't see them on the field together, though, unless the WRs just completely tank and they need two receiving-first TEs out there.
If healthy, I'm calling for a Wisnieski breakout. He's 6-5, 250 and can run.
In your video clips, Fant looked like a WR going into and coming out of his breaks. Very fluid and explosive.