I don't mean to hijack the thread but I have literally the same question. I have a young newly purchased juniper, which seems really healthy, but the pot is more like a drinking cup with a drain hole. I don't want to rush things but I don't want having the wrong pot giving me trouble in the future.
I was kinda leaning towards the pot being too big or too deep rather. I was thinking the same thing about the stones ill take them out when i get home. But yes it is outside on my apartment balcony facing west. Only option available for outdoor.
the answer to repotting? No. it was growing strong, then I decided it needed a bigger pot to gain some girth. that killed it unfortunately. instead of trying to apply bonsai techniques to baby trees, ive been spending my time learning about how to just take care of them properly. things are going much better now lol