What do You mean by no consistency of component selection icons and component snap icons?
The wrench on the tab is filled, because hollow one was visually not strong enough against the other icons.
Regarding Object icon - a lot of time spent on symbols analysis and their visual compatibility, many projects of whole sets of pictograms corresponding to the Object icon and referring to it, a sea of words and a very valuable contribution of active Blender users, preceded the current design. The modest form of this icon is perfectly coordinated with the other pictograms. Adding the third dimension (making it a 3D cube) will not bring quality. It’s already here.