Julra’s Obssesion is a tricky example for this kind of stat.
Technically this does not give “minion cast speed”. So you will not see it on your character sheet.
All the stats on the gloves are simply inherented by all your minions, so they get “%inc cast speed”, which is not detailed anywhere.
This is very simialr to how forged weapons and manifest armour inherents bonuses from items.
All these “minions” simply get those stats for themseves, but its not you (the player) who gives them minion ralted stats.
Another example to make this more clear. (or probably confuse you :P) If you have something like “%inc minion health” on your Julra’s Obession, your minions will benefit from this, because your character will get an %inc to all its minion health.
But this stat inherented by your minions will NOT give them anything (unless they have minions themselves. Now your minion minion’s will have additional health, because all your minions have this “%inc minion health” as a stat as well.
I think this is intended so there’s no double-dipping of bonuses. If you had increased minion damage on the gloves, then the minions would get it once, and then again for the inherited function of the gloves.