I don't know who was the genius behind this change of InDesign file icons, but it's very time-consuming, most of the time i will open the IDML file instead of INDD file or viceversa. Probably for people working with few files is not a big deal, but when you work with tens of files, it's a hassle to constantly need to check the file extension. It cannot be changed from Explorer, you need a third party tool to do this on Win 10, which i don't wanna use.