Is there a word for this cultural phenomenon?

This is known as the (logical) fallacy of

affirming the consequent

or the 'converse error', which is the error that, given that B follows from A, one can infer that A follows from B. Surely if it rains then the ground will get wet. But if the ground is wet it does not necessarily follow that rain was the cause.

This is related to the general correlation fallacies including 'post hoc ergo propter hoc' (the fallacy of thinking that f B comes after A, then A caused B).

I don't know if it's a cultural phenomenon, but it seems like the definitions in your example are subjective interpretations of the true definition. Perhaps "subjective(ly)" comes close to the meaning that you seek.

the word "Christ" is often subjectively defined. It takes on different meanings in every individual person's mind.

The presumption that "wealth is an obvious sign of hard work and thrift" is a subjective assumption at best. Wealth is not necessarily defined by those qualities.

https://www.thefreedictionary.com/subjectively