Most rich people setup DAFs alongside their family foundations so that they can make large contributions to this type of org. without triggering disclosure or private foundation tests -- so e.g. Musk will create a DAF at Fidelity Charitable and give them $100M and collect the associated tax break in year 1 -- he can then direct Fidelity to grant $20M/year to OpenAI which will show up as Public Support since it's coming from another nonprofit entity and Fidelity maintains ultimate discretion over the funds.
Nice work. The IRS proposed regulations in 2017 that contributions from DAFs should be treated as if they came directly from an individual donor, but they are still waiting on final regulations.
Since private foundations aren't public charities, they don't have the pass-through protection of donor-advised funds, so this should have been excluded from the public support total because it is more than 2% of the total support.
Edit - Got curious and sure enough - this is the 28,000 page 990 filing for Fidelity Charitable: https://apps.irs.gov/pub/epostcard/cor/110303001_202006_990_...
On page 205 there's a $3.5M donation to OpenAI from 2019.
Likewise here for SVCF on page 237 (https://apps.irs.gov/pub/epostcard/cor/205205488_201912_990_...) - there's a $30M donation to OpenAI in 2019.