Boosters don't really "explode". When ruptured they burn really fast, but (assuming engine shutdown and non-malfunctioning capsule separation) at such high altitude there is not that much danger from simple conflagration.

Sure, in _very_ rare case engines might not shut down or something else might get broken, but "If the booster had exploded, the crew would have been in extreme danger." seems too over the top. Launch escape tower is jettisoned for a reason ...