I have no opinion on them as this is the first time I see them but their misrepresentation of Amdahl's law bothered me as their version makes it incorrect to the point of being useless. Here's how they present it:
T(n) = b + (T(1)-b)/n
T(n): Time to run task for n parallel threads (workers)
b: Time it takes to run part of task that can not be parallelized
Therefore:
T(inf) = b
This misses the cost of coordinating between workers. It also removes the key part of it being a theoretical limit of the speedup as resources increase.
Their attempt to simplify it makes the new version dangerously wrong if you take their word for it.
Less wrong:
T(n) >= b + (T(1)-b)/n
Or even (but now it's not really Amdahl's again):
T(n) >= b + (T(1)-b)/n + C(n)
In fact, for many problems T(n) > T(n-1) for some n, as at some point C(n) > (T(1)-b)/n
This is not really "a more subtle improvement", "new version", or "refinement". It was known in the field in the 70s. That is, Brook's Law can apply to parallelized computation, not just to teamwork. Which OP observes but still doesn't make them see the errors in their previous assertion.