Transposition is an L-derivation which only transposes a lexical item from one lexical class, i.e. N, V, A, to another. For example, the deadjectival nominalization which generate importance and creativity from important and creative, respectively, adds no semantic content nor modifies any inherent feature of the underlying A; it merely changes the adjective into a noun. The meaning of important is simply 'having importance'. The nominalization allows that meaning 'importance' to be expressed as a referential term rather than as a quality.
The LMBM definition of transposition differs from the morpheme-based theory's in that it is not limited to words that transpose with no morphological marking (affixes). The definition here is purely semantic. Thus LMBM does not have to explain the absence of affixation on "transpositions" like (to) cook → (a) cook, where the meaning shift is "coincidentally" identical with the Agentive Nominalization. Under LMBM this shift is simply an Agentive Nominalization without affixation, in other words, zero morphology. Since affixation is separate from derivation, LMBM derivation simply ignores these differences.