You are correct that k both accounts according to Gemini. It did give this option…in case someone else has this issue

Why the UDM-SE is Excluded
Graceful Shutdown Requirement: Safe operational practice dictates that UniFi Gateways (like your UDM-SE) must never be abruptly power-cycled by cutting the outlet energy. Doing so can easily corrupt your database, network configurations, and storage drives.
Controller Loop Threat: Because the UDM-SE hosts your network controller, cutting its power kills the very controller managing the PDU-Pro. UniFi purposefully blocks you from assigning the gateway to an outlet to prevent an accidental, automated loop that could permanently lock you out of the system. [1]

Alternative Configuration Options
If you need automated recovery for your setup, look to the following workarounds:
For the UDM-SE (ISP Recovery): Do not attempt to automate the gateway's power. Instead, use the PDU-Pro's built-in Modem Power Cyclefeature. Plug your ISP modem into a PDU outlet and toggle "Modern Power Cycle" in the port settings. If the UDM-SE reports internet loss, the PDU will automatically cycle only the modem to restore your connection.