IFR Student: Why do you have to advise centre of your departure runway?
IFR Instructor: You need to know what runway any inbound traffic is using, if someone is inbound on an RNP, opposite direction it puts you head to head.
IFR Student: Makes sense.
IFR Student forgets to transmit departure runway to centre.
Centre doesn't ask IFR pilot what runway they're using.
Safety occurrence, never followed up by anybody, until it's two jets at a 3rd world airport in a first world country.