This makes you unable to give your Spirit Bear an item if you spawned it with an illusion, e.g. Hybrid of allied Lone Druid, Morphling's items are muted on the Spirit Bear spawned by his own Hybrid illusion. Or a Vengeance illusion of Rubick, who steals Spirit Bear from an enemy Lone Druid.

Repro:
1. Pick Morphling and get Aghanim's scepter and a few other items
2. Create an allied Lone Druid and level up Summon Spirit Bear
3. Cast Hybrid on the allied Lone Druid
4. Cast Summon Spirit Bear with your Hybrid illusion
5. Put items on your Spirit Bear

Result: The item you give your own Spirit Bear are muted. It only accepts items from its summoner, which is the Hybrid illusion itself (but illus cant drop or give items)

Expected: The Spirit Bear should accept any item which belongs to the player, and not only items which belong to its summoner.




Alternatively, instead of Morphling and Hybrid, you can also test it this way

1. Pick Rubick, level up Spell Steal and get Aghanim's Scepter and some other items
2. Create an enemy Vengeful Spirit and level up and use Nether Swap
3. Steal Nether Swap from Vengeful Sprit
4. Drop some of your items, but not your scepter
5. Get your Rubick killed
5.1. You now have a Vengeance illusion because you have aghs and had Nether Swap on death
6. Create an enemy Lone Druid and level up and use Summon Spirit Bear
7. Steal Summon Spirit Bear with your Vengeance Rubick illu
8. Summon the Spirit Bear with your Vengeance Rubick illu
9. Pick up your previously dropped items with the spirit Bear

Same result as above.