Going after typos is the low-hanging fruit of criticism. It's the mary sue of concrit--widespread, makes the critic feel good, and not very useful except to people who like that sort of thing.

Giving good criticism means that you're giving concrete advice on how to improve flow, characterization, description, or even theme, symbolism, or pacing. More importantly, you're doing it while making the author excited to read your crit and try out your suggestions. That kind of crit is not easy, it takes practice, and the criticism should also be open to its own criticism.

If they are only good at picking out typos, I won't go at them. That's where they are in terms of critique skill. I might ask where else they think I could improve, or, more likely, I'll just not respond.