"That tells me that no data is flowing directly into the IRS computers from this form (there will likely be a flag generated saying that Form 8915-F is "attached" which may be enough to ward off nastigrams later)."

Yes, that is what is going on, because the IRS schema info has stated in the file "Known Issues and Solutions:"

"Form 8915-F, Qualified Disaster Retirement Plan Distributions and Repayments was not developed in XML for TY2021 as expected. Software developers who cannot attach a PDF binary attachment can use a 'GeneralDependencyMedium'."

And it can happen behind the scenes:

"Form 8915-F, Qualified Disaster Retirement Plan Distributions and Repayments, will be accepted in MeF as a PDF attachment for tax year 2021. “Form8915F” must be used as the binary attachment description when including Form 8915-F as a PDF attachment."

"Schema will be developed for Tax year 2022/Processing Year 2023"

And that is dated December 9, 2021. I previously copied this info to this forum in the past, but there are too many topics on "Form 8915-F" to copy it into all of them.