Calypso: Viewer role users not searchable by email on simple sites

Quick summary

The search feature in Calypso (WordPress.com > My Sites > Users > Search bar at the top) does not return accurate results when searching for viewers by email address or username on Simple Sites. This issue appears to be specific to the "Viewer" role, and it occurs regardless of the site's privacy setting. The problem does not replicate on Atomic sites.

Steps to reproduce

prereq. Set the site to Private status, otherwise the Viewer role is not available.

Navigate to WordPress.com > My Sites > Users.
Ensure there are users assigned with the "Viewer" role.
Use the search bar at the top and attempt to find a Viewer by entering their email address or username.

What you expected to happen

The search feature should return a list of users that match the entered email address or username, including users with the "Viewer" role.

What actually happened

The search does not return any results when searching for Viewers by email address. It seems to be working inconsistently for usernames.

Impact

Some (< 50%)

Available workarounds?

Yes, difficult to implement

Platform (Simple and/or Atomic)

Simple

Logs or notes

The user who reported this issue: 6369117-zen

The issue appears to be specific to the "Viewer" role and is not affected by the site's privacy settings (private or public). It could be a bug within the Calypso user search functionality specifically related to Simple sites. More testing is needed to determine if this is an isolated issue or more widespread.

A video showing how I could reproduce this issue can be found here:

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Automattic / wp-calypso