Although it does not suck out the moisture of the air as it sounds, it does reduce the humidity of the air. Because the air is heated, its capacity to hold water vapour is increased, thus reducing the relative humidity, which is what our everyday use of the word humidity means. With a lower relative humidity, evaporation and transpiration happens at a faster rate, it has a similar effect of less moisture in air of the same temperature. The snake would still have shedding problems and get dehydrated.
Such as heating air in the winter, where heating indoors always seems to make you excessively thirsty and dry, but step outside and you don't get that same effect. I have tried this, I have air with a humidity of 60-70% all year round, but with the lamp on the humidity reading inside the enclosure can drop by up to 30% lower than this. This cannot be due to the dry air coming into the enclosure, but because of the decrease of relative humidity (even though actual water vapour level is unchanged). Relative humidity is what causes the transpiration, evaporation and dehydration, not the actual moisture levels.