Okay, this query was easier to put together than I thought!
If we include all accounts that have at some point owned a name that currently points to an account that has its reverse record set, we find 11,520 accounts that would receive a total of 1,776,717 additional tokens.
This seems overbroad, though; if you owned a name and sold it, or let it expire, and the new registrant set a reverse record, you would both get the multiplier. A fairer metric would be to require that the address had held a name that pointed to an account that had that name set as the reverse record at the time the user owned it. Calculating this would be much more complex, and I’d like to see if there’s an appetite for going further with this before putting a substantial amount of time into researching it.
(Alternately, if anyone wants to take a look - the relevant tables are available at ens-manager.airdrop and ens-manager.names in BigQuery; I can also provide the queries they were constructed from.)