I had an interview a day ago, the interviewer asked me about phases of SDLC.
Well, the important thing in the question is to be sure you understand the world beyond your nose. Of course you're not directly impacted by the SDLC, but still, 80% of the shop around you will be. In other words, the recruiter asks the question to ensure you are able to get out of your role, and see things as a whole.
That's important for your career to be able to know things beyond your own role. It helps a lot in senior roles, and sometimes even in junior ones, when suddenly you have to cooperate with the team nearby(be it product development, specs writing, commercial, whatever...).
Not only you have to answer the question(as excellently explained by Niels), but you have to appreciate a company that tries not to lock you into a closed role - and therefore give you more cards to play for the next move in your career path.
Of-course you should a try to answer all questions in a job interview and if you don't know you can answer that you don't know, much better then making up bullshit. It might be good to openly question how this question relates to the job offering if you think its outside of the scope of the actual job.
In this case with SDLC I would expect all team members in a software development team to have a basic understanding of software development lifecycles and what their part in it is. Thus I think this is a perfectly valid question to ask an automated tester.
With answering any question you could try steer towards something else like the STLC and explain how this more important for you as an automated tester.