The Swiss, Austrian, and Danish leagues are hugely underrated in that table. Croatia's is overrated. Strange that the Serbian league isn't there too.
Also they've clearly underestimated the Azerbeijani/Kazakh leagues, which have had lots of silly/dodgy money thrown at them in the last few years.
A UEFA table of leagues (team performance in Euro comps, past 5 years) agrees that the Futhead table underrates Austria (5 spots) and Denmark (6 spots), and overrates Greece and Croatia (5 spots each). Switzerland ranking is only one off, so not a bad correlation overall.
Wondering which are the best leagues for recruiting imports, looking at wages vs strength of league - maybe the South American ones?