That'd be great. But it isn't possible. File feedback to Apple. Maybe we'll see it some day.

This piqued my interest. I tracked down the plist setting and without extensive testing this appears to maybe have done the trick.

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
<plist version="1.0">
<dict>
    <key>PayloadContent</key>
    <array>
        <dict>
            <key>DiscoverableMode</key>
            <string>Contacts Only</string>
            <key>PayloadEnabled</key>
            <true/>
            <key>PayloadIdentifier</key>
            <string>com.apple.sharingd.9a8471fe-dfde-42d8-aa8b-8758fb728154</string>
            <key>PayloadType</key>
            <string>com.apple.sharingd</string>
            <key>PayloadUUID</key>
            <string>9a8471fe-dfde-42d8-aa8b-8758fb728154</string>
            <key>PayloadVersion</key>
            <integer>1</integer>
        </dict>
    </array>
    <key>PayloadDescription</key>
    <string>Lock Airdrop to Contacts Only</string>
    <key>PayloadDisplayName</key>
    <string>Airdrop Settings</string>
    <key>PayloadIdentifier</key>
    <string>com.apple.sharingd</string>
    <key>PayloadOrganization</key>
    <string>TEST</string>
    <key>PayloadRemovalDisallowed</key>
    <true/>
    <key>PayloadScope</key>
    <string>System</string>
    <key>PayloadType</key>
    <string>Configuration</string>
    <key>PayloadUUID</key>
    <string>04c17696-b0c4-46e6-9261-ea9f5c4bd643</string>
    <key>PayloadVersion</key>
    <integer>1</integer>
</dict>
</plist>

Has anyone able to get this to work? I'm pushing that plist with my device's UUID on 12.5 and it doesn't seem to do anything.