The stars created by the star cloak do not enter your inventory when picked up. They should act like mana stars enemies drop, hearts enemies drop, and nebula pickups. Which don't lose thier grab range when your inventory is full.
I think you're also getting this confused with the celestial magnet, that's what give pickup range to stars dropped by enemies. Mana cloak is a completely seperate item, it creates star pickups when you take damage, you collect these to restore 50 mana, these are uneffected by the celestial magnet. The fact that these pickups lose grab range with a full inventory is what the bug is.