Mind that even in their first example, "The results of the study were quite (important | significant | substantial | notable)", the meaning is by no means interchangeable.
"Important" refers to impact, "significant" to the statistical qualities of the underlying hypothesis, "substantial" to the work involved, and "notable" is a referential judgement by the speaker. The implied normalization of words and their respective meaning also marks one of the mechanisms how "slop" is typically creeping into the productions of "broad verbose interchange replicas" (it's all interchangeable, and a choice isn't really that, a choice, isn't it?).
"Important" refers to impact, "significant" to the statistical qualities of the underlying hypothesis, "substantial" to the work involved, and "notable" is a referential judgement by the speaker. The implied normalization of words and their respective meaning also marks one of the mechanisms how "slop" is typically creeping into the productions of "broad verbose interchange replicas" (it's all interchangeable, and a choice isn't really that, a choice, isn't it?).