Not quite. Apparently he didn't pose as the runner in order to take a drug test, he borrowed his ID to get into the athletes' village (not all coaches and staff have been allowed full access). While he was there, he (well, Rotich) was tagged for a random test. Instead of just admitting he wasn't Rotich, he took the test... but it's obvious he isn't Rotich.
And Rotich took the test as soon as he found out, which was apparently only a few hours later. It still speaks to the attitude and approach that Kenya takes to doping control in general though. He clearly thought this was acceptable, and given he's a coach, the mind boggles.