I think that one end must be wrong.
Why must it be that way?
From the UNECE Agreement:
E 15 Inverness – Perth – Edinburgh – Newcastle – Scotch-Corner – Doncaster – London – Folkestone – Dover ... Calais – Paris – Lyon – Orange – Narbonne – Gerona – Barcelona – Tarragona – Castellón de la Plana – Valencia – Alicante – Murcia – AlgecirasThe English Chunnel Terminal is at Folkestone, a place where, as defined in the Agreement, the E15 explicitly continues beyond to Dover.
The '...' is not a guarantee of a crossing (and many don't exist in any form), as it is an agreement about roads not about sea crossings, so the French signing E15 to the Calais Chunnel Terminal is perfectly acceptable.