I didn't like it either. Luckily you can disable it in settings; Settings shortcut: General > Expanded Toolbar

IIRC that space is a standard design attribute of Android's "Material You"

So you can reach the top one-handed

A bit of space is nice sometimes, especially around titles

IMO it's a non-problem, because it's not permanent, it dissapears if you start scrolling and enables you to reach it with your thumb