Interesting idea. Microsoft used that same reasoning to change all of the office apps, Visual Studio Code icons. Here is a before and after on macOS.
Being of a certain age and watching the ever changing UI of macOS over the last 30+ years I’m not sure we should hold up Apple’s UI team as the pinnacle of UI as we once used to. There seems to be little thought any more of actual Human Computer Interface (HCI) when developing these user interface items. It baffles me that a development team would want their icon to “blend in” and to look like everyone else’s icon. Wouldn’t you want it to stick out from the others, to make it more easily identifiable to the users? Since there are no words (unless you hover over the dock) the ONLY thing that allows a user to find an icon that they are looking for is visual identity of that icon. That includes the colors, the shapes, the sizes. If you make your icon look the same as every other icon then that adds unneeded mental gymnastics to just locate and launch your application. It isn’t about “… it looks better in the dock”, but about “… does the change relieve the user of any extra work” and in this case I would vehemently argue that is does not.