There are so many different ways in which an ATCO will do something – 20 controllers will handle a complex busy situation probably 20 different ways and they have to keep changing their plan since the traffic situation is constantly changing.
That's inevitable. Every so often I get asked to do something that I've never been asked to do before, and it throws me. That doesn't mean the request shouldn't be made, but it's worth bearing in mind that the further from standard behaviour something is the more likely it is to cause confusion and error.
A go-around is a fairly well rehearsed manoeuvre even for a solo student, and the need to apply climb power is obvious. But the instruction to make a turn off final may have confused (particularly about the level he was supposed to fly at) enough to leave the student in a quite unfamiliar power/pitch/configuration/flightpath combination.
Standard procedures are never going to cover every case. But if we can find standard procedures that work, we should use them.