I've read in a number of places on the net that the WinSCP file mask *>1D only selects one file. First of all, is this mythology or true? If the latter, how does it work? Does it select the latest file or the first one that meets the criteria. More importantly, if it's true and there is more than one file that meets the criteria, how would you select and download all of them?
No, it's definitely not true. Where did you read this?
The confusion may come from the fact, that the above mask can be used (and is used) to select the (one) latest file, but in case there's one file per day added only. I.e. you have some scheduled process that produces an output file once a day and you want to select and transfer that file.
In any case, this use is just a hack and should be avoided. Proper solution is covered in article Downloading the most recent file. Basically, you can use the -latest switch of the get command.
But in general you are right, the mask selects any number of files that were created or modified in the last 24 hours.