Um, the possibility that your *ahem* "educational video" may not be
proportionally correct?

..seriously though, care of niceties such as
DDC, the card'll know what it's being connected to, and adjust its output accordingly. If not, there are solutions to get around the problem but, considering that widecreeen LCD is so common "out there" (as in USA), it's a well catered-for format.
-bdt