The likely culprit, so to speak, is not just the freezer but rather the mill of the bag within which the bread now comes. Any relatively thin sheet of plastic is actually porous at the microscopic level. That's why you can smell right through some of these bags and detect what's in them, or detect the poor or better condition that their contents are in. Who for example cannot identify raisin bread with nothing more than a whiff of the bag? So even the slightest reduction in the mill [of a plastic] can yield an exponential increase in its permeability.
Now it may be, yes, that you noticed this change at or around the time you replaced your freezer. This concomitance is probably not irrelevant. Nonetheless, the marketplace is always looking for ways to cut costs, especially in the United States. And when you think about the sheer number of plastic bags that are involved nationwide for annual bread sales, the slightest change in the mill of the bag equates to some very real dollars.
I noticed quite recently here a change in the packaging of my milk cartons, (half-and-half actually), obvious because of the dramatically different color. But the carton is now so thin you can feel it caving in as you pick it up. I also noticed that the screw-on lid was lighter in weight as well as thinner in its construction, (bendier and more translucent), and that the amount of turn required (and therefore allowed) was reduced. In short, it was a complete overhaul.
Okay, that synchronized cluster of changes didn't just happen for no reason. There are always motivations at play, especially when multiple changes have to be authorized by multiple layers of individuals at multiple levels of responsibility. What were those motivations? Was my grocer's provider (dairy) just feeling generous? Did they mistakenly ascertain that I as a consumer (speaking generally) would pick up this flimsier version of a container and respond in something of a positive manner?
Of course not. They didn't do it for me (us). They did it for themselves (profit). That's the pattern. That's the die that is cast. And that's more probably what accounts, at least in part, for the difference you've noted and shared. In my example, the carton supplier [to the dairy] could increase its profit margin over time and still manage to offer the dairy a slight reduction in cost for, say, every gross of cartons. Not complicated. Everybody wins but the consumer. Same deal for the mill of your plastic.
Certainly I don't mean to force this as an only explanans. The freezer too is bound to play an important role as follows. You did say it's a newer model frost-free, meaning newer than the frost-free you said you had before. On that note alone, here's what seems a likely scenario.
A frost-free works, obviously, by drawing not only the heat but the moisture out of the freezer. It does so nearly constantly, and on a very low level. That's all that's needed. So heat's being drawn out by the compressor (cold is just the absence of heat). And moisture's being drawn out by way of an evaporator and one or more fans.
The use of an outward drawing fan action creates a slight negative pressure. This pressure builds over time and then peaks, because the fans are only just so strong. By dint of this, note that the freezer door can at times be surprisingly difficult to open. A pressure differential has formed between the two sides. So anything in the freezer from which water can be drawn is going to be subject to these forces and will, of course, capitulate ...or as the Wikipedia article on the subject states,
water can evaporate out of containers that do not have a very tight seal,..
This fact in combination with the risk of too thin a mill in plastic, (where too great a porosity is synonymous with a poor seal), would serve to perhaps best explain the results you've experienced. The solution as you've suggested is to contain the loaves of bread yet further, probably placing them in large freezer bags. Beyond this, no doubt there remains something to be said for the kind of refrigeration which does not worry itself over the matter of frost build-up. Anathema!, I know.
Another consideration is the possibility the bread is being quickly transitioned from a decidedly warm environment (such as the trunk of a hot car), straight into the freezer. This itself would cause slight condensation, (difficult to notice as it's absorbed by the bread), as here the permeability if the package works in reverse, initially drawing in water from the freezer. (There's always evaporated water in the air, air which can enter the freezer whenever the door is open, including for example water from our own respiration.) In short the noticeable brittleness of the bread crust would follow not only from having the moisture pulled out by the freezer, but from the fact that it was actually pre-moistened one step prior.
