The trends are based on the TYPO3 major versions statistics. Note, that a large amount of TYPO3 websites have been removed from the database in 07/2020 and 10/2020, because some scenarios were not covered by the TYPO3 check. Also no new domains have been crawled in 07/2020. Therefore trends may currently indicate a wrong tendency.
It is planned that future major version statistics will always include a full crawl of huge domain lists, so trends will be more accurate.