It depends on the job and mostly on your level of experience relative to their requirements. When I was very first entering software engineering, self taught, most of my interviews went like you’re describing. I had built a few apps which I was proud to demo, and usually they’d ask me to build something in 8-12 hours according to their spec.

I wouldn’t do it NOW, but just starting out it was actually a lot of fun and I learned some neat tricks along the way. That kind of interview landed me a great first job and launched my career.

So I wouldn’t consider that a red flag all by itself.

However I would push back if the scope they ask for is unreasonable, ie if it would take more than a Saturday or so.