Missing author filter on Atomic sites

It was reported in 4835937-zd-woothemes that the icon to filter posts by "Me" or "Everyone" went missing on My Site > Posts. During testing, I noticed this happens only on WPCOM Atomic sites. Also, worth noting that the filter exists in the WPiOS app.

Expected behavior

I would expect to be able to filter the post and page lists in the app when there is more than one author on the site.

Actual behavior

The author filter option doesn't show up in the app.

Steps to reproduce the behavior

1. On the WPAndroid app, select a WPCOM Atomic site that has posts and pages authored by more than one user.
2. Go to My Site > Pages or Posts, noticed that the author filter icon doesn't show up on the top left corner of the screen.
3. Select a WPCOM Simple site that has posts and pages authored by more than one user.
4. Go to My Site > Pages or Posts, noticed the author filter icon appears on the screen.

Screenshot taken on a WPCOM Atomic site

Screenshot taken on a WPCOM Simple site

Tested on Pixel 4, Android 10, WPAndroid 19.2

Start by reproducing the missing author filter on an Android WPCOM Atomic site with multiple authors, then compare the Pages and Posts lists with a WPCOM Simple site and the WPiOS behavior described in the issue. Done means the author filter appears and can switch between “Me” and “Everyone” for both lists on eligible Atomic sites.