There seems to be a bug in Unity because ScrollView.mouseWheelScrollSize does affect the ScrollView differently in edit mode and play mode. Tested on Windows 11, Unity 2023.2.3f1.
[Info :XUnity.AutoTranslator] Version of TextMesh Pro: 1.4.0. [Warning:XUnity.AutoTranslator] Could not hook 'TMP_Text_SetCharArray_Hook3'. Likely due differences between different versions of the ...