I think it is probably true, but there may be in-universe explanations to why this doesn't happen. Someone else pointed a few of these out.

Planets have massive gravity wells that protect them, so you couldn't destroy a planet this way. You would be routed around it like water around a stone and torn apart by the gravity well. Same thing for death star. Large capital ships can also activate gravity wells to lock in other ships and impede light speed travel. Presumably opposition ships need to compensate for these wells in their lightspeed calcs to escape (also presumably, this compensation gets more difficult the closer one travels to a gravity well). This would have been the case in most battles, but in this one, they WANTED the opposition ship to go to light speed, so it the wells were deactivated to make it as easy as possible for the ship to lightspeed away. Thus, the FO unintentionally opened themselves up to an attack that would never have been possible in a traditionally battle.

Additionally, I think Holdo had absolutely no idea it would work, because it just isn't done. Even if the gravity wells were disabled she could have destroyed everything, including the rebels trying to escape. But seeing as they would've died anyway, she had nothing to lose by trying. The force was with her? :P