For example, the statement that tall parents will always have tall children is incorrect, though there is a strong bias. I would be curious to see how the probabilistic linkage between parent and child height compares to that for language. My guess is that parent language has a stronger effect than 99.9% of SNPs identified in GWAS.
If you really think about the difference between the two inheritance scenarios you outlined, it's that one mechanism of influence occurs at a scale that readily admits direct observation and perturbation while the other doesn't.
I don't think we (humans) know anywhere near enough about how genes compare and interact with other factors to support an argument either for or against your final statement.