Bourbon, even though it does appear that Blackrock added a ton this quarter, unfortunately that is not actually the case. Assuming you are using data from whalewisdom.com like I am, It looks like for some reason they (either WW.com or Blackrock) consolidated all of their subsidiaries under 1 filer this quarter. Similar to what Fidelity/FMR did in a past quarter if I recall. If you consolidate all 12/31 Blackrock ADXS holdings vs 3/31 Blackrock Inc holdings, it looks like a slight drop of 26k shares, which is a similar change to previous quarters. Also looking at the 13F filings for BR Inc for 3/31 and comparing to prior quarters, you can tell that the fluctuations stand out pretty drastically.
I have always relied on data from whalewisdom to be accurate but now I am starting to wonder. Still not sure if it was the way the website reflected it on their side or if it was an actual filing change from Blackrock.