I think this is the right line of thinking. My understanding of the grandparent's argument is 2 pieces:
1. Heterogeneity/homogeneity of labour.
2. Tight/lose labour market.
I think Argument 1 is the weaker argument. There's a lot of fungibility between software roles. However, there's a higher learning cost. Moving to a new software company requires a few months before someone is close to full productivity. This in contrast between a painter moving from a Ford supplier to a GM supplier will likely close to full productivity within a few weeks. The cost (to the employer) is lower to rehire someone.
Argument 2 is the stronger argument, but may not be forever. In a tight labour market, I see very little need for unions. If the marginal worker can (and will) leave their position for a better position (pay, benefits, culture, etc), I see little need for unions. However, if the labour market for software engineers shifts in favor of businesses, this will change rapidly.
1. Heterogeneity/homogeneity of labour.
2. Tight/lose labour market.
I think Argument 1 is the weaker argument. There's a lot of fungibility between software roles. However, there's a higher learning cost. Moving to a new software company requires a few months before someone is close to full productivity. This in contrast between a painter moving from a Ford supplier to a GM supplier will likely close to full productivity within a few weeks. The cost (to the employer) is lower to rehire someone.
Argument 2 is the stronger argument, but may not be forever. In a tight labour market, I see very little need for unions. If the marginal worker can (and will) leave their position for a better position (pay, benefits, culture, etc), I see little need for unions. However, if the labour market for software engineers shifts in favor of businesses, this will change rapidly.