This sounds like an offshore recruiter. I work with several and some are just blunt to get the info needed, and rate is a big part of it. if that lines up they can go further in the discussions but it saves them (and you) time from a long talk that goes nowhere due to rate. I wouldn't consider it a red flag but be aware they likely have a handful of others that got the same email.

Also, FYI for future negotiations. Don't start with, "I won't take less than..." You're setting the bar on how little they can pay you, and you don't want to do that. Do some research on what the job pays for your education, experience, and skills and start there. It's fine to say something like, "My target rate is $25/hr but I'm open to discussions depending on the details of the position."