Yeah.
To rephrase what


Magman said, when a bomber has a target, it will fire at it whenever it is in it's firing arc, regardless of its altitude.
The situations where it bombs without diving usually occur either when an attack is given as it is flying above its target, leaving no time to dive, or during a multi-target attack if the bomber was previously targeting a static structure and has no time to dive when the target is suddenly switched (usually when the structure dies to another bomber)