Jasper saw the Crystal Gems, if she was allowed to go back to Homeworld she would've told YD that "Rose" and her army were still alive.
Some may argue that Jasper's corrupted and can't tell them. But as shown in the new ep, the Rubies (or at the very least one of them), is a competent Gem. They could've told YD about them, probably after their primary mission. But now Navy might just retrieve the other Rubies and tell the Diamonds directly.