A teacher out of union is still as much working class as is a teacher in a union. We software engineers are working class because we have to work for our money.
Do you own businesses, land, investments, and other forms of capital that generate wealth independently of direct labor? Enough wealth so you don't have to work for the foreseeable future? Is this the average software engineer for you (in or out of a union)? Because that's the definition of NOT being a part of the working class.
They enjoy more benefits and compensation than if they were not in a union. Most importantly more protections.
Comparing those in unions who are more likely to be in the video game making or industry or government to faangs like Amazon where you work day and night for a 4 year vesting offer that pays out very little until the 4th year and where on average most worker work less than 2 years at Amazon.