Look at box count, not revenue
The ODMs only had 9% market share, but this translates into perhaps 20 to 25% of units shipped, since ODM boxes are really inexpensive compared with EMC and HPE. Another factor here is that the customers of the ODMs typically buy drives direct from their makers, while the others include expensive drives in their revenue numbers.
In other words, ODMs are eating up the market faster than we think. IDC needs to get up to date on how it reports all of this.