Maybe they know something we don’t about Ed25519? [Queue X-Files theme tune]

Maybe their organisation has a policy that requires stronger encryption? Possibly because that organisation is also in the business of cracking such encryption...

Is Ed448 stronger than Ed25519?

Quantitatively, yes(2^224 security target vs 2^128 security target respectively wrt. discrete log calculation).

Qualitatively, 2^128 is already computationally infeasible(barring some advance in quantum computing), so the meaningful difference in security is debatable, assuming no weaknesses in the underlying curve.