Apple's method of naming files has been lousy from the start - you get a photo from something digital and it is labelled as something like D7K_2242 as noted by thedatadude elsewhere in this thread. My first mistake when I uploaded to iphoto my photos was to assume that if I changed the title, it changed the photo name. Reseting my camera by deleting all the photos after upload, a different D7K-2242 would eventually come up, be titled as something else, but when I eventually burnt a DVD of photos for a friend, quite afew went AWOL, because the same file name overwrote the previous one!
Having learnt my lesson, every file is renamed before it goes into iphoto/photo, to something like 20170524 San Francisco A 08 - YearMonthDate (Location or event) (letter if I have lots of photos on that day) number within the sequence. If I want more data attached to the photo, I use faces, keywords, and very occasionally a description. I used to be able to see those photo names as the default title in iPhoto
Transferring from iPhoto to photo, all the names are gone, although the titles are still correct. But you can only see them if you open info, as it displays non-existent titles instead of defaulting a blank title to the file name.
For new uploads, I am wasting my time when I upload and doing faces by highlighting the file name (minus the ".jpg") copying (Command-C) and pasting into title (Command-v). Far from ideal. If someone knows how to do this with an applescript or similar, I'd be greatful, for those who have different titles, you'll need another solution.