I agree, and I'd go as far as to say that the author is a bit confused and showing some confirmation bias. Let me explain.
Engineered wood indeed creates elements from imperfect timber that are free from defects and exhibit the same engineering properties, if not better.
This has absolutely zero to do with old vs new growth trees. It is exclusively due to the need to maximize the amount of wood you can take out of a tree. Old growth trees might have more wood to pick and choose from, but nothing stops anyone from using the exact same techniques with timber from old growth trees.
The only reason why you don't see as much old growth trees in this process is the fact that there aren't that many anymore.
Another reason why you see new growth trees being used extensively in engineered wood products is that you can put together massive structural elements from smaller lumber elements, and they are far cheaper and plentiful.
There's a story on how the renovation of Oxford's dining halls required massive oak trees which were hard to come by, but it turned out those who built Oxford's dining halls had the foresight of planting oak trees when they built the structure. They did so because they knew the beams would eventually have to be renovated.
https://longnow.org/ideas/humans-and-trees-in-long-term-part...
With engineered lumber you do not need to plan centuries ahead to have your structural elements. You just build the elements you need from the timber you have at your disposal.