I'm just guessing here. But couldn't Titleist build a mini-driver with a very low center of gravity? Then it would work off the deck. The deep face wouldn't be as problematic.  I'm just spit-balling. I know nothing about this product. 

Yea, but a deeper face makes it not as useful off the fairway. This is why the driver is not easy to hit off the fairway.  For a select few PGA Tour players, it might be good. The concept of the mini driver has been around for a long time now. Very few ever keep it in their bag. This is a guess, but probably because it sucks off the ground. Nothing here looks like it is any different than the other mini drivers of the past.  I get it from Cameron Young and Will Zalatoris point of view. They hit the ball a long way. The odds they ever hit a 3-wood off the turf is like what, a handful a times a year? They probably would hit it 98% off the tee and 2% off the ground. They probably want something that think is longer off the tee versus their 3-wood because they don't hit the 3-wood off the ground much at all.  This is where I say, Titleist claiming "worked as a go-to club off the tee and off the deck." is more marketing than something that is actually beneficial to a golfer. This is primarily for off the tee.   

One thing I've noticed with Mini Drivers is that the manufacturers seem like they keep their quantities somewhat limited.  The last two TaylorMade Mini's and the Callaway AI Smoke Mini were sold out quickly. 

Huh? That's the niche of these mini-drivers. They can still work off the tee and off the fairway. They're designed for and work for both things, which is all that blurb says. You can see from the photos that it's a bit of a deeper face, which I find is more important off the tee than the fairway.

This statement doesn't make much sense to me.  So, I think the push and pull between a 3-wood meant for off the turf versus off the tee is how tall the face is on the 3-wood. I do not get how this mini driver would be good off the turf, or at least get the height needed to stop the ball as a normal 3-wood meant for off the ground. Maybe they care more about hitting the 3-wood off the tee versus off the turf. Nearly every strike would be low on the clubface relative to the CG location.  I would take that statement as more as marketing over what you would actually expect the club to perform.