MarkB
Legend
Although... when do you ever have a combat/encounter that lasts 1 hour in-game time? Unless the encounter mostly involves talking, which is already covered under "light activity". I'm tempted to read that as fighting, casting spells or 1 hour of walking, i.e. a short battle = 1 hour of walking, and both would interrupt rest.
I go with the more generous interpretation - It's talking about those activities in combination, not necessarily doing just one of them the whole time. Basically what it's saying is "if your camp is compromised and you have to relocate or re-secure it, maybe fighting and spellcasting along the way, so long as you don't take more than an hour about it you can pick up where you left off."