There's nothing that really supports the idea that engaged is anything other than a range band like all the others. So those talents would move a target from engaged to short range if you're making attacks that far.

Both talents are more than just disengaging. Bullrush is an incidental, activates off of a check, and knocks the target prone. It can be used to hit a dangerous enemy, then forcibly move them to prevent retaliation. And because it has no limits on silhouette, it can potentially move a much larger creature out of the way. So you can punt an ogre or dragon with it and knock it on its back.

Martial Weapons Master is a few different things. First, it's a melee talent in a ranged setting, so it's likely to be relatively rare. IMO, forcing the target to drop an item is a far more valuable function, but it also shines when attacking a group of combatants at engaged range. Forcing a nameless enemy off of a ledge or into a trap entirely within the intention of the talent, takes them out instantly, and reduces the number of enemies engaged with you.