Edgington !
I can only imagine that as the TAP a/c was heading in a E/NE direction, if
he was already near Groningen before EuroControl decided to send interceptors - then they are as near as dammit entering BRD airspace anyway, and the Germans could then probably carry on the escort as far as Luebeck or beyond with DK permission...... a short stint from Groningen by NL fighters would have seen them in BRD airspace rapidly anyway....
Just my theory - no inside knowledge ........