treasure box drop rate

Hi everyone! I've been doing some treasure hunting, and I've noticed that the drop rate for "better" items (that is to say, not mats) are significantly higher when you open a box with 10 keys (max amount of keys), as opposed to opening the boxes with less keys.

Whenever I use a key when I have 10 keys, I usually get orb shards, ava tickets, etc. But afterwards, (9 or less keys), I usually get mats or revitas.

Is this a coincidence or does everyone else notice this? Can someone also tell me if the drop rate for crystals are higher when you open the box with max keys?

 

always got mats with nax keys.
the good stuff appeared after opening many boxes, usually when keys were low.

 

Its all RNG lol