It's not just "a 90-day ban on immigrants coming from war-torn countries" - the fact that Christians from those countries are exempt makes it explicitly a "muslim ban".
No, 'explicitly a Muslim ban' would say 'this is a ban on Muslims'.
Do consider that the list of proscribed countries is compiled between the Departments of Homeland Security and State, not by the President, and is published in the Federal Register. The fact that the majority on that list currently coincide with dominant Muslim populations might have been useful for Mr Trump's intent but is not guaranteed to persist.