In Perspective, dropdowns stop scaling down their height once they reach a certain minimum size of about 40px. In the designer you can see the outline of the component get smaller than the minimum but the actual dropdown extends out of the outline, similar to how the text in a label extends past its height and width dimensions.
This is particularly a problem when a view is in percent mode and the user makes the web browser smaller; input components such as text fields scale down but dropdown components hit a certain point and stop scaling which makes a lot of things misaligned/really ugly.