Yes users have to clear the browser history. I logged a support call with ESRI UK and they have given me a bug reference. There is no update on whether or not it will be fixed. If you log a support call it may add some weighting to the issue.
BUG-000144885: When working with the user's own identity provider (IDP) in the ArcGIS Field Maps mobile app, SAML logins are cached, preventing a new user from logging in when a previous user logs out.
BUG-000144885 for ArcGIS Field Maps (esri.com)
The workaround for it is currently the following steps:
- Log in to ArcGIS Field Maps on the mobile device through the SAML login.
- Log out of the mobile app.
- Clear the browser history.
- Logging in now prompts for credentials, and another user can log in and use the ArcGIS Field Maps mobile app.
This workaround is only possible if there is a browsing history to clear.
We have also blocked access to Office365 apps on shared devices until this is rectified which far from ideal.