An accountant will tell you that a loan with an unconditional obligation to buy constitutes, to all intents and purposes, a permanent transfer and should be accounted for as so.
That's completely correct. Some guidance from PwC here to verify that...
However, if that a loan has an obligation which is conditional on some sort of target being met, it can't be accounted for immediately as a permanent transfer as there is no certainty that the transfer will become permanent.
In Röhl's case, the loan has an obligation to buy next summer, on the condition that we are not relegated (according to the reports in Germany).
Because of that condition (and it's why conditional obligations are common in a PSR-avoiding way), we aren't accounting for any of it until next season.