Maybe I missed a minor detail somewhere, but I didn't get how the 3 "heroes" started time traveling...obviously Anna Faris' character had something built in, but its never explained how the eventual bearded guy went to take a pi55, started singing an 80s tune and wala...time traveler?
I can suspend a little belief for comedic aspect, but most of the time traveling was pretty straight forward.
-- I'm your average ordinary everyday, jorgeegeetooo!
How do we know it didn't? Pete at one point finds the bones of other humans at the bottom of the hill, or it's also plausible that because the time leak was in direct reference to them and their future they were the only ones effected
Less like time travel ( when you know which direction you're going and have a destination in mind ) and more like SLIDING ( random jump to a parallel universe that you have no clue about it's history ).
You are describing a method of transportation, which might be called "slipping" ("Timeslip" is often used in japanese storieS) or "sliding", if you prefer. But it's still traveling. Traveling by slipping, traveling by running, traveling by automotive means, traveling by magnetic propulsion, traveling by teleportation - it's all TRAVELING, just utilizing different methods.
Traveling is a larger concept, 'sliding' would be a small detail OF that concept.
So, it's still time traveling. Even if you travel by catapult without knowing your destination, you are still traveling.
"Travel" encompasses a wide palette of all kinds of different methods. Just because one method is less usual than some other, doesn't mean it cancels out the "traveling" bit.
"Sliding/Slipping" is still just as much 'Time Traveling' as using a DeLorean with a flux capacitor installed, operating an incredibly limited (only four numbers) panel to choose a destination is.
Having said that, I kind of like the word "Timeslip", and wish it was used more. But "Frequently Asked Questions about Timeslipping" wouldn't have sounded as accessible, I suppose.
The time leak caused them to time travel. It was due to Milly's interference in the timeline. The whole reason Anna appears is to fix the time leak that causes the boys to time travel. I'm really not sure how you could possibly have missed that.