Why did the desktop icon's link overlay change?

For a very long time desktop's way of indicating that a file is not on desktop but at some other location was by overlaying a simple arrow at the bottom of the desktop icon's bottom that you see on several items on this desktop image here:

Recently it has changed and here is how it looks now. There is a tiny image overlayed at the same location where the arrow from former times existed as shown.

The question is why?

This is a change driven by function, not just aesthetics.

Cloud services like OneDrive, Dropbox, and Google Drive needed a way to communicate the status of a file. Is it synced? Is it a local copy or a cloud-only file? Is it syncing right now?

The old arrow overlay didn't provide this information. To solve this, these services created their own icon overlays that appear on top of the standard file icon. The "folder-like" or other new icons you're seeing are probably one of these:

Details:

A folder or cloud symbol: Often indicates that the file is not a local copy, but an online-only file. This saves space on your hard drive. The symbol acts as both a shortcut indicator and a status indicator.

A green checkmark: Means the file is fully synced and up-to-date on both your computer and the cloud.

blue sync arrow: Indicates that the file is currently in the process of being synced.

A red "X" or exclamation point: Signals an error with syncing.

These overlays are a more modern, layered approach to icon design. They allow the operating system to show multiple pieces of information (is it a shortcut? what's its sync status?) in a small, visual format.

So, the change wasn't from a simple arrow to a simple folder. It was an evolution from a single-purpose icon (the arrow) to a more dynamic, multi-purpose one (the arrow plus a status icon). You'll still see the classic arrow on most shortcuts that are not managed by a cloud service.

This said, there are files that carry the arrow image overlay on their icons in the more recent desktop display shown above. Those items have no shortcut key as shown in their properties shown here: