There are clear distinctions between these subsets and successful deception can require both to be present.
Concealment is passive, it is NOT saying something, so nothing has to be made up. This means it is less drain on cognitive and emotional resources. Often in concealment, the liar may feel less guilt and find it easier to rationalise.
Concealment is easier to cover up as there is no long story involved. You do not need to remember the beginning, middle, and end of a story that you have made up in case you are asked about it again.
Due to lack of cognitive engagement required in concealment, it can also be the most difficult type of lie to detect.
Falsification, on the other hand, is when something is completely made up – a false encounter. It may be in relation to future intent or a past activity.
Falsification is much harder to do than concealment and it requires much more brain power. Not only must the liar come up with a convincing story, they must also now remember the details of what has been said in case they are asked about certain details again later.