The upload date of the file does not change whether you choose "just replace" or "replace, use new file name..."
I can see some rational for not changing it for the first option but it would seem useful at least for the second.
There are several pdf's on a site that are updated several times a year, every year. It's helpful to have the date showing in the media library updated.
Since I haven't seen anyone else mention this, it looks like I have a feature request and not a quirk.
plugin has been working well through several versions and it's use has been intuitive for several users. thanks.