To my knowledge, Seedlip never uses the word hydrosol; instead, they seem cagey about what is in the bottle, and that’s a different flavor of dubious.
It’s easy for us booze drinkers to be dismissive of non-alcoholic drinks, but there is a real need even if it’s not really being met satisfactorily. A non-drinker wants something that tastes good and where they can feel they’re included and not stuck holding a glass of something juvenile.
The gold standard, as far as I know, is the non-alcoholic menu at Existing Conditions. Those booze-free drinks are sophisticated and tasty, if eye-bugging expensive. They’re also not make-at-home.
The best luck I have had is with shrubs—those bring booze-level flavor intensity, some complex flavors and aromatics (mainly from the vinegar), and usually a bit of color. The limitation of shrubs is that they inevitably taste like shrub.
There’s a vast trove of temperance drink recipes from back in the 19th and early 20th Century—I probably ought to give them a serious look.