Since one entity can have multiple addresses of multiple sizes, I don't know if any chart (or any conclusion) based on balance sizes can be accurate.
So, sorry, but I find this yet another attempt to find correlations.
It could be the result of an exchange breaking down their balances or something similar. Hard to say for me, as I don't waste time worrying about what others are doing with their coins. I have seen this statistic touted many times recently though, as the chart is astounding. However, I think if it were the result of a major entity distributing their coins across multiple addresses for whatever reason, some chain wizard would have likely identified this and made it known that's what is happening. So I have no reason to doubt that it's legitimate growth of the userbase.