The GNOME 40 is under development at the moment. And a recent change on App Grid functionality shows that it now scrolls horizontally.
If you use GNOME, you probably already know that until now GNOME always had the App Grid scrolls vertically. That means today, you have the App Grid page indicators at the right side like this. And it scrolls vertically with a mouse wheel or touch devices.

GNOME 40 App Grid Now Scrolls Horizontally

With the recent changes, it seems the App grid page indicators now at the bottom. And you can scroll it horizontally. See the above image. Remember this is still Work In progress and yet to be merged after proper testing.
From the Aesthetically and usability standpoint, it is natural for us to scroll horizontally for touch devices. You tend to swipe horizontally than vertically for touch devices. But not sure how it feels when you scroll using the mouse wheel. Because mouse wheels are vertical and it would scroll horizontally.
From the merge request, it is not sure whether it is permanent, and no way to enable the vertical scrolling after this is implemented. It would be better is the team allows an option to switch between both the mode of scrolling. If not, then we need to see whether this can be tweaked via the GNOME Tweak tool or dconf editor.
What else coming in GNOME 40?
GNOME 40 is due to be released in March 2021. There are already some new features already tagged to this release.
GNOME 40 making the multi-line icon texts show completely when focussed. This makes it easy for those applications whose names are longer.
GNOME 40 also making changes to the GNOME Extension ecosystem with the “Extension Rebooted“. Every time, after a fresh GNOME release, many extensions break. And the developer needs to work on it and make a fix. This probably going to change as the GNOME team is streamlining the extension model so that the developers can easily test their extensions with the new release codebase before the final release. This is going to be beneficial for the end-users and the overall GNOME ecosystem.
Don’t forget to check our coverage of the detailed GNOME 40 features, released dates.
Image credit: GNOME; Tip credit: baby Wogue