dc heroes time travel

From the DC Heroes "Powers & Skills" book:

"Superspeed gives a character the ability to move . . . at speeds faster than humanly possible. . . .

"At [a score of] 30 . . . or more, the character may Time Travel. With a speed of 30 APs [the standard unit of measure in the game] or more, a character may travel to any time period, either past or future. He may not change what occurs - he many only observe."

Wow. I know comic books have used the time-travel-through-speed thing before, but I didn't expect a game to say, Sure, do it. I pity the GM whose player uses The Flash, say, to time jump all around whipping up some real Bill-and-Ted's shenanigans.

And by what law of time travel do they figure characters can only observe other time periods? Is the speedster not actually there? Is it just a rule to keep things from becoming too messy? If so, why allow for time travel at all?

This seems like a poorly thought-out thing all around.