A strong opinion does not have to be about what tech stack to use for best results, that depends on the goal. It could also be a few notches above the actual tech. My strongest opinion would be about the usability of what I'm creating, not just what the user wants but to figure out what they really want. Sometimes they are so blind to the actual problem that the solution they want isn't quite fixing the problem in the most efficient way. Especially if they don't know enough about the tech to know other ways of fixing the workflow to their liking.

That's almost a non-answer in the context of an interview for a technical role.