1) The TextField height property is significantly less than the visual height, and also less than the similar looking ComboBox.  In Dense variant, the difference is 12 pixels.
Hence, when you manually override heights, you have to make the TextField height 12 pixels less than a ComboBox to make them look the same.

2) In Qt 6.4.3 (Material 2), the default ComboBox and Button heights (including visual) are identical.
In Qt 6.6.1 (Material 3), the default heights are different, and now the new TextField needs to be considered too.

3) Possibly a side-effect of fixing placeholder bugs, the top of the TextArea box can no longer be easily anchored/aligned without introducing a magic number offset for this style only (compare with Universal, for example).
In my opinion, the Material placeholder is the special case amongst the different styles, and users could add extra padding if they choose to use it.

The above issues make Material 2->3 migration more difficult than it could be, especially when you have these controls in the same row, where the visual differences are more obvious.