Parkinson's law seems off to me w.r.t. Tog's paradox. Were it true, Tog would be silent because nothing would ever get more complex.
> that work expands so to fill the time available for its completion
If it's restated as "that the worker expands time spent so as to fill the time available to them", it comes in line. And is more in line with my observational experience. People like to do things in their job. If the "job" gets easier, people invent "job+", and Tog's on the money.