macOS Mail - Insert from iPhone or iPad greyed out

I was trying to insert a photo into an email using macOS Mail, and the 'Insert from iPhone or iPad' option in the File menu was greyed out. Similar facilities in Messages, Pages, Numbers, Keynote are all working fine.

I worked around it using Universal Clipboard, but I'm wondering why was the obvious feature not available?

2020 M1 MacBook Pro 13" on macOS Ventura 13.6.1 fully updated

iPhone 11 Pro Max on iOS 16.7.2 fully updated

Both devices with WiFi, Bluetooth and Handoff enabled.