I just ran the query with 2021-10 data:
SELECT COUNT(distinct page) AS num FROM `httparchive.response_bodies.2021_10_01_desktop`
WHERE REGEXP_CONTAINS(LOWER(body), r'<meta\s+([^>\s]+\s+)*name=["\']?monetization["\']?')
The result is 1275 out of 5,531,644 pages, or 0.023 %, so it looks like it has increased a lot in one year!