There are two meanings to "gene" here. What you describe as lego blocks are segments which code for a protein, which is one meaning. The other is just any code

There are two meanings to "gene" here. What you describe as lego blocks are segments which code for a protein, which is one meaning. The other is just any code which affects the phenotype, including promotors etc. The SNPs mentioned in TFA are just known fairly common single-point differences, but aren't necessarily in coding DNA. Of course these are still heritable, just like coding changes.