That method doesn’t work for Mautic 4 and above, and especially not for Mautic 5 and 6, because the hashing algorithm used to store passwords has changed.
The hash value they give you:
a5b253d8484925a3b4fba260768416dfdcbeaed639bb3435c566cbf54721f846903725c7283cf9ab1f090f179d015f46a50b5e798695547eda6e2342db8918a2
is a simple SHA512 hash, which is no longer compatible with how Mautic generates and verifies passwords in modern versions (it now uses password_hash() with bcrypt, and may also include a “cost” option).