SE are not working class. At best they are at the top end of the middle range, and generally above 100k is considered 'upper middle'.

The idea of SE as working class is from categorization based on labor relations, not on income.

In a Marxist-theoretic framework, for example, SE are clearly working class.

Software engineers quite often have and derive substantial income from capital holdings; when they do they are, in a Marxist framework, of the petit bourgeoisie (the middle clsss between working class [proletariat] and major capitalists [haut bourgeiosie].)

But, yes, some software engineers are working class, as well, the profession largely being split between the proletarian intelligentsia and petit bourgeois intelligentsia.