Nope there are no winners in this one . Not only can the same workbook be opened by different users, you can accidentally open the same workbook twice on your own machine, unwittingly make changes to both (Alt-Tab can be a brutal fast) and save both, stepping on each other, and losing half your work! (Does this sound personal? Yep it is.)
So take great care managing who has 'control' and not destroying each other's work.
That is what I thought. Just wanted to be sure. Thanks!
One other warning just for good measure:
When doing Save As SLOW DOWN & look. Most Windows programs default to the directory/folder the file was opened from; not Tableau. It defaults to the last Save As directory used. So you end up with lots of out-of-place workbook scattered everywhere throughout your directory/folder structure. (I know this, and still keep doing it!)