It’s just data.
If someone were to replicate this exact experience the unit count would be different in total and from each crystal type. each crystal type has a 15% unit chance drop. It’s pure RNG at the end of the day.
700,000 Battlechips spent on each arena Crystal type available is a fair sample size.
At the end of the day you decide on converting your saved up Battlechips on the arena crystal that suits you.
https://youtu.be/SOtD44xT2fA?si=IxjsVhZ84aKOHGJy