simultaneous bombings

why are simultaneous bombings always deemed to be a sign of a technically sophisticated terrorist group? it seems to come up a lot. like in today's NYT article about the recent bombings in kampala:

But other terrorism experts said that running a clandestine operation in Uganda, which lies hundreds of miles away, on Kenya’s western border, requires sophistication, as does pulling off simultaneous bombings, at a rugby field and an Ethiopian restaurant.

i can't say i've ever tried to bomb anything, so i'm no expert in what makes an attack technically challenging. but once you have the explosives it seems to me that making them go off simultaneously wouldn't require anything more sophisticated than a clock.