Meetings run over all the time. In fact, you might say that that's their natural state. Meetings think gases are lazy. Whereas a gas expands to fill its container, a meeting expands to exceed the size of its container.
It requires good management skills to keep all your meetings on schedule. And it takes great management skills to get them all to finish early.
Even someone with poor management skills sometimes valt met je gat in de boter and a meeting will finish early by some fluke. And unfortunately, I've been at meetings where the meeting organizer decides that this is not an acceptable state of affairs.
"Okay, it looks like we still have ten minutes, so Bob, why don't you tell us about Topic X," where Topic X might be "how your part of the project is doing" or "the meeting you had with Team Y." Whatever it is, it's something that wasn't on the meeting agenda. It's just there to fill time.
Of course, it takes Bob fifteen minutes to talk about Topic X, because a meeting expands to exceed the size of its container. What started out as a meeting that came in early turned into yet another boring meeting that ran over.
There's no law that says a meeting can't end early. If you're finished early, then finish early.