Do you know what Google's incentive was for participating in those meetings?
They were pretty guarded and cagey about everything to be honest. Felt like a favor from a trusted internal contact but our contacts there would not share any details and mostly listen and occasionally confirm our guesses if it was public knowledge. Our meeting agendas were always prepared well in advance and very intentional.
Imagine a scenario where the original image was linked in the page as “main.jpg” or “flower.jpg”.
There may or may not be useful signals on the page for Google to infer from. In the case where the image is saved on Pinterest, the title may come from an expert user who submits, “Trumpet Daffodil”. This is a lot more precise and searchable.
We would go out of our way to append keywords to the end of page and image filenames to make those even more relevant. A final file name for this image would be, “eb761df34b9219ffc68e5c9e55a134f0—-trumpet-daffodil.jpg”