After sending this to mechanic @ Ford (Ford said the TSB isn't the right # but it is a known fix to that warning message), they said this should fix that issue:
TSB #48268 - 2020 Explorer/Police Interceptor Utility - Discharged Battery/No Crank - Built on or before 30-Aug-2019. The Bulletin states, "Some 2020 Explorer/Police Interceptor Utility vehicles equipped with SYNC built on or before 30-Aug-2019 may exhibit a discharge battery/no crank condition. This may be caused by the software in the accessory protocol interface module (APIM), body control module (BCM) and/or the telematics control unit (TCU) module. To correct the condition, reprogram the APIM, BCM, and the TCU using the latest software level of the appropriate Ford diagnostics scan tool. If the BCM software update is not available in the FDRS Toolbox, a software fix is being developed. As a temporary fix, uninstall and reinstall FDRS selecting 'remove all data'. If the battery drain concern is still present, follow normal diagnostics in Workshop Manual (WSM), Section 414-01 > General Procedures. Effective Date: 17-October-2019."
The mechanic said 2 of the 3 device softwares were already up-to-date. They updated the 3rd (BCM) needed updating. Haven't seen the error since but need to test this on a long trip again to be certain.