Inefficiency, in the Economic Sense
These tests are necessary, but should not be put before a phone interview. The interview process is a two way street. The candidate wants to know what you really need. Over the years I have had many short and sweet (under 3 minute) phone interviews. At that point I was able to say, "Thank you. I'm not the guy you're looking for, and here is why." To do that, I had to talk, yes talk, to the person doing the hiring. Not the recruiter, not a test.
Requiring a half hour investment up front (4x30 minute questions is half an hour for a qualified candidate) eliminates candidates who budget their time. Take a test and learn nothing about the position, or go outside and play? Easy choice.