Getting captions added in MacOS Photos to appear in iOS photo

I have begun copying the title to the caption for my photos in MacOS Photos, hoping to then sync the caption with the photos on my iPhones and iPad. I found an AppleScript on the community that automates the title-to-caption copy process in MacOs and it works, i.e., I can see the correct text in the caption field when I look at the Photo info after running the copy script.

I'm adding the captions so I can search on captions on the iOS devices.

I don't use iCloud to sync, I sync the phones and iPad with a physical cable connection.

• I added captions to a dozen photos in one album on the MacBook Air that are currently synched in all four devices (MacBook Air, iPhones, and iPad).
• I physically linked and synched one of the iPhones, and the captions didn't come across.
• I changed the removed the album from the list of synched albums, and synched again. As expected, the photos were then removed from the iPhone.
• I added the album back to the list of synched albums, and the phots were added back to the iPhone, but still no captions visible on the iPhone version of the Photos.

Is there a step I'm missing to update the photos on an iOS device to include the new caption? If not, any other ideas how to get the captions to the iOS photos without hand copying them on each iOS device.

iOS is up-to-date on the iOS devices, and I'm running latest version of Big Sur on MacBook Air due to age of the MacBook.