Why does the cursor type vary?

All applications in Mac OS and their web interfaces on iCloud vary with their cursor type. My question is for the same apps, why does the cursor type vary between the OS and Web?
Please refer the screenshot taken from Pages-…
Button Icon States

I’m currently trying to determine how buttons with just icons as placeholders should be represented throughout our product.
Currently, each button is displayed as the representation on the right in this image.
I’m curiou…