Well, it turns out this is a duplicate of: Setting up Neos with XAMPP - Community / Newcomer’s Corner - Discuss Neos – the official forum of the Neos project
And my guess above is wrong. See Setting up Neos with XAMPP - #5 by ReHa01 for the solution ;D
made an issue: composer create-project neos/neos-base-distribution fails on windows · Issue #59 · neos/neos-base-distribution (github.com)