I belief that sentence to be broadly correct. First and foremost, it is making a comparison more than an absolute statement of fact. And (without having first-hand experience), it doesn't seem obviously wrong to say that someone who left for an extended vacation in 2014 would have more surprises waiting for him today than a mechanical engineer who did the same from 1926 to 1929.

Note also that the statement is also talking about the "half life", indicating an understanding that there is a part to expertise that is less susceptible to aging. One can criticize that the concept of half life is misapplied, because the underlying process isn't stochastic, i. e. that half of knowledge will not again half in another half life. But then one would be splitting half hairs, which of course is one of the engineering skills that never go out of date.