It's just as frustrating for us as it is for you. File it fly it is fine as long as you can actually get to the filed level. Being stopped lower for traffic reasons or aircraft load issues can and does push you into different sectors that can get overloaded. Happens very regularly from CLN/NOR London sectors into Maastricht.
I'm presuming that this EASA directive (which I haven't seen) is the root cause of London not being able to offer cross border directs this summer into Europe. Thus causing more frustration on the parts of pilots expecting them and the ATCOs that want to use them to help the sectors run more effectively.