Wesper Hardware Engineer interview questions

The interview process took about 3 weeks total in July 2020, and in the end, I let them know I was no longer interested in continuing the interview process. There was an initial phone screen (non technical), followed by a technical video interview with the engineering VP. After the video interview, there was a 'take home' project to be completed and then reviewed with their entire team. According to the interviewer, the project should take about 3 days time, but can be spread over the course of up to a week to be completed. Initially, I was very excited about the company, the team and their project. It was actually a pleasure to speak with both interviewers on the phone and video interviews but when I had read through the assignment and gave it some thought, it seemed very detailed and in depth for an interview. I've heard of interview projects before but this is the first time I've received one myself, so I emailed the interviewer back to ask what the results of the project would be used for, and if we could change the scope of the project to something less detailed. Instead of a transparent reply and answer, they told me that, "if [I] was implying that they are using the interview process for free labor, then [I] must not think much of [their company.]" They also did not want to change the scope of the project (fair, it's their call and just a suggestion on my part). Now my opinion: The interviewer's reply to my question is the biggest red flag in this interview. A valid question was asked and instead of answering, they were evasive and defensive. It shows how your future manager would behave if their employees ever voiced a concern to them or if there's a difference of opinion. Later I checked Glassdoor and saw others felt they were being used for free labor. I don't know if that's Tatch's intent at all, which is why I asked, but it seems like their interviewing style is giving off that impression to others, which should tell them they might want to rethink their interviewing process. The way I understood project interviews in the industry is that they generally take a couple hours at most, and the content of the project should never be able to be mistaken for something that can be used in a company's product.