KB article https://kb.isc.org/article/AA-01309  has now been updated with a note explaining how this change will affect the frequency of root re-repriming

4770. [bug] Cache additional data from priming queries as glue.
Previously they were ignored as unsigned
non-answer data from a secure zone, and never
actually got added to the cache, causing hints
to be used frequently for root-server
addresses, which triggered re-priming. [RT #45241]

-- fixed in 9.12.0, 9.11.3, 9.10.7 and 9.9.12