Professional designers can't afford failure, so they make "safe" designs that are likely to work. This isn't a result about "knowledge diversity", it's a result about incentives.
I am not sure that holds up at least in the German market, most boardgames are what most other industries would consider failures with maybe 2000 copies sold and hardly breaking even if you would consider all the hours put in.
You make some money with semi-hits if they are licensed in our contries as you basically have no further effort for income.
The only big money pot is hitting Spiel des Jahres.
That is a plausible hypothesis. However, without any research backing it up I wouldn't be so dismissive of the conclusions of paper that actually put in the legwork to test its own hypothesis, without even engaging with the content of the paper.
I engaged with the paper. They didn't do a controlled test of anything. They ran some stats on BoardGameGeek.