Why is Apple music "Top Charts" different from iTunes "Top Songs"?

Hi, all.

I like to occasionally search for new, popular music. My go-to list is the "Top Songs" listing on iTunes. I am an Apple Music subscriber and would prefer to do this within the Music app on my phone. There, under "Browse," is the "Top Charts" listing. Why is that listing completely different from (what appears to me to be the far more accurate and helpful) "Top Songs" listing in iTunes???? It would make it A LOT easier for me to download and listen to the top songs if i could access them directly from within the Music App.

Thanks!