False. If you increased the sealing of the house and did nothing to ventilate or control moisture generation, humidity would build up and force more moisture through the unsealed cracks. But window condensation and air quality demands forces us to keep the humidity in the house to a constant comfortable level. (search keyword "condensation" for the title "WHAT IS THE SOLUTION TO CONDENSATION PROBLEMS?") Thus, the quantity of moisture going through a given crack will not change even if a crack on the other side of the room is sealed because we use other mechanisms to keep the relative humidity in the house at acceptable winter levels. Sealing as many cracks as you can will not make matters worse for those areas that you cannot reach.
If you can seal the whole house, it is advisable to start at the top of the house and work your way down. The cracks higher up in the house are the ones that have hot moist air leaking into the attic and walls. The cracks in the bottom of the house get more of our attention because they are bringing in cold drafts, but from a condensation point of view they are less important and they will even slow down if the air can't escape out the top.