[R-pkg-devel] Problem with "additional repository".

I have submitted a new package to CRAN, and this package has been
knocked back on the basis of a NOTE:

* checking package dependencies ... NOTE
Package suggested but not available for checking: 'ionChannelData'

This suggested package consists of data sets, the size of which is too
large to satisfy CRAN's constraints. I put this package in a repository
on github, from which it can be accessed by users.

My DESCRIPTION file contains the line:

Additional_repositories: https://rolfturner.r-universe.dev

The given URL seems to work, in that users can indeed load the
ionChannelData package via the command

install.packages("ionChannelData",repos="https://rolfturner.r-universe.dev")

I was under the impression that this was all that I needed to do.  The
CRAN checking process acknowledges the existence of the repository in
question:

Suggests or Enhances not in mainstream repositories:
   ionChannelData
Availability using Additional_repositories specification:
   ionChannelData   yes   https://rolfturner.r-universe.dev

So CRAN knows about this repository.  Why can it not make use of it?

What can/should I do to resolve this problem?

I guess I could simply *not* Suggest ionChannelData.  But what then, is
the point of the option of including an Additional_repositories field in
the DESCRIPTION file?

cheers,

Rolf Turner