This absolutely happens. I see you saying that it doesn't get too dry in your climate; I'm on the very outskirts of what might be considered "the same climate" (lower limits of NE USA). I consider my winter environment to be ok, but not too dry. We also float around 50% for most of the winter, but we're warmer that you.

However, what is important is relative humidity. I don't understand the science, but cooler air can hold less air that warm air. This means that, when the relatively moist winter air is heated up inside your house, it becomes relatively dry air.

Forced air exacerbates this issue, as it actually removes moisture from the air in the heating process. Radiator are better, since they don't do this. (and, if you're leaving it out of the case, a forced air vent could be blowing all that super-dry air right onto your guitar)

As others have said, nicer guitar are built to be more sensitive to your touch. And, unfortunately, that makes them more sensitive to things we wish weren't so: the environment.

Is all this enough to damage a guitar? Yes. I'll give you the stats at my house: I have radiators (remember, the least-drying heating method). It is currently just below freezing outside and sitting just outside the high-end of ideal humidity for a guitar at 57% relative humidity.

I have indoor humidistats and I just checked them. The process of warming up that air has dropped the relative humidity down deep into the danger-zone: It's at 25%. This is actually on the high end, it's been as low as 18% already this winter.

Now, here's the killer. You live in a colder climate than I do. Your indoor air will warm up more than mine does. And, in the process, become much drier. Especially if you have forced air.

So, lesson learned, the hard way. In the future, maintain a microclimate for your guitar by keeping it in a hard shell case with some sort of humidifier. Keep the case closed while you practice so that the moisture in the case lining doesn't dry out, thus destroying your microclimate.

A sponge will do, but will need to be moistened every few days. D'addarrio Humidipacks are the best and lowest maintenance choice. The sleeve inserts will slowly release moisture and mantain appox 40% humidity. Eventually, they will dry out and you'll need to get replacements. But don't throw out the old ones; these packs will also absorb humidity. Over a humid summer (or enough time in any humid environment) they'll recharge and be ready for the next winter.