I was about to post a support question about failure to sync, but it turns out that in fact I was too hasty, SyncThing did synchronise what I was attempting to sync, which is good. But it does raise the question, what are the different ways for to confirm this?
What led me to believe sync in fact hadn't occurred was that the internet speeds on both ends of the sync are generally pretty slow, so even for a relatively small file, I'd expect to have been able to see a change in the 'up to date' status in real-time. Also, the 'latest change' section was and is still reflecting a change made some time ago and has made no mention of the addition of a new file from my end or the successful synchronisation of that file with the other end.
I wonder, is there any kind of SyncThing equivalent of the Dropbox 'ticks' that allow one to determine the synchronisation status of individual items in a shared folder? Also, is there any longer (but still human readable) list of changes than the one-line 'Latest Change' section of the GUI? I also wonder, should I be seeing anything in the latest change section for having added a file to the folder, and successfully synchronised it? What type of actions are reported in the 'Latest Change' section? The change it currently reports as the latest was a deletion from the remote device, should I expect only to see reports of the remote device's behaviour? It was they who shared the folder with me so I guess that makes sense if so, just unclear.