You got that exactly right. That's why they can reverse themselves on nearly every major issue over the course of years or decades, and still be 'progressive'.

Progressives, or rather leftists, in my country used to be anti-immigraton, because it depresses workers' wages, pro-car, because they wanted every worker to have a car, anti-war, critical of Big Pharma, critical of the weapons industry. Needless to say, there is none of that anymore.