Linear progression is a good concept, it assumes that things go from stage 1 to stage 2, then to stage 3, and eventually reach the final stage. However, the fact that it is simple and nice does not justify its correctness.
In real life, many things do not go through linear progression, say the development of the country. One may argue that a country can only develop according to the sequence of stages in the development model, i.e. pre-industrial, industrial and post-industrial. However, this may not be true for some countries which jump from pre-industrial to post-industrial by some alternative ways. Also, common linear progression has an end point which is definite, but this can be a belief rather than a fact. For example, a U.S. citizen may think that capitalism is the end of the stages for ideology, whereas a PRC citizen may think communism is the real end. Clearly if the perceived end is different, the progression is not clear any more. A U.S. citizen may claim that U.S. is at the final stage of development, whereas a PRC citizen would reject that and say U.S. has yet to go through socialism to reach communism.
In fact, building on that idea of indefinite end, we will never know if the progression has come to an end. For example, current computer technology has evolved to a stage where ordinary people can get access to a computer easily. Is this the end of the progression for computer’s accessibility? I think not, one possible subsequent stage of development would be a “computer” planted inside each person. And even at that stage, we cannot conclude that we have come to the end of the progression.
Progression can also be in terms of humans’ development. A person goes through different stages as he/she grows up. It would be logical to think that everyone follows a linear progression of life, biologically, from young to old. However, the real maturity of each individual may develop in a non-linear progression. Some people grow up with care and love from parents hence slowly turn from immature to somewhat mature, then finally mature. Others may not have such privilege, they have to become mature immediately because they do not have such luxury of time to go through transition before facing the serious world.
Now if we take a step back and redefine linear progression as always going from early stages to later stages(like jumping from stage 1 to stage 3 and skipping stage 2, but not the other way round), would it be perfect to fit everything inside? It appears so. However, now the hard part would be to define the stages clearly so that they follow a total order. Progression like EQ or maturity are hard to define stages as there are just so many factors to consider.