Synapse Health Lead Software Developer interview questions

There was the initial HR interview that lasted 30 minutes. It was pretty straightforward. Then an email comes a couple of days later with a really specific tech assignment. They asked me to take a piece of trash one file .Net program and turn it into a production ready application with unit tests in .Net 6. It took a couple of nights to complete. Then I had a run of the mill tech question interview from two directors. - Name a design pattern besides Singleton. - Dependency and inversion of control. - Order by vs group by. - Some questions about discipline and dealing with people. Really run of the mill stuff. They said they were going with someone more aligned with them. However, the job was reposted. Due to the specificity of the assignment being production ready and the reposting the position, I have suspicions this employer may be using tech tests for free labor.