imo its much more important that we have a test in phpcr-api-test that covers this case. if somebody has to time to run the test suite and look at code coverage and think if we have situations that realistically can happen (like this situation) that miss a test, that would be very good indeed.
regarding sprintf versus string concatenation i have no idea what it means in terms of performance or code style or anything. does Psr1/2 or symfony coding standards say anything about it? if they have one we should follow it, you could raise the question on symfony-devs dan, so there is at least a tendence, before we normalize one or the other way.