impossible. OpenCV doesn’t look at FPS when reading video files. there is no mechanism that would “pace” the reading because nobody wants that. I’m sure you’ll get an error code when you even try to set such a property on a VideoCapture of a file.
the only backend that is even capable of causing such shenanigans is gstreamer and even then one would need to do something explicitly and specifically wrong. I saw one instance of such an issue in the past 5+ years. nobody else ever reported that again. probably because the person back then wrote their own gstreamer pipeline and made a mistake there.
the more likely explanation is that OP generated a hypothesis that’s close enough to reality (video only appears to “play back” close to realtime), then latched onto the hypothesis without considering alternatives.
especially when you haven’t used VideoCapture on files before, please be careful with generating more unsupported hypotheses, or believing and feeding into the first unsupported hypothesis. doesn’t help anybody, only adds confusion to the both of you, and any passers-by looking for answers that’ll find this later.