Oh I bet the head will be undersized. HT seem to have a habit of doing that for some weird reason. Even allowing for the mass of hair it still does seem a tad small in all the promos so far.
Yes, sometimes HT heads come out undersized for their figure bodies, for whatever reason. They can be hit or miss.
While Jack may indeed look undersized in the end, I feared ill-proportions on the Barney Ross figure from this photo, tiny head again.
Yet the in hand figure just looks absolutely perfect, so I haven't totally committed to Jack being flawed in this regard.
I really wouldn't compare head size with a picture like that, not only is his legs in a different position, but the Hot Toys TT body isn't specifically sized for him, unless he's actually 6' tall.
While comparing where parts of Johnny line up to the figure isn't the best thing, you can argue the size of the figure head relative to the body, in that photo it just seems too small, it's like a 7 foot person's body with a 5 foot tall person's head, but again, I felt the same about Barney and to my relief I loved the figure I got so I'm not going to throw in the towel over HT's photos.
One thing I've found with figures, they can be flawed in some ways and those flaws will show in photos and make certain shots hard to get looking good, but yet just looking at them with your eye, those issues aren't so apparent. Like Sideshow's Darth Vader and HT's T-800, there are things that certain photos will highlight and make the figures look just awful, but when I go to set the shot and am just looking with my eye, I see something really nice. The most important thing in the end is that when you look at it in your display, it looks right to you, if you can't take certain photos without it looking bad, oh well, you live with not taking the shots, your display look is what ultimately matters most when you're buying these.