Acquia is aware of an issue impacting CLI upload_max_filesize and post_max_size for customers running PHP 7.3 or 7.4 in an Acquia environment. Impacted customers may be limited to a max upload size of 2M or 8M when processing files via cli (e.g. drush).
A workaround available to customers while Acquia prepares a platform level fix is to configure an override in ~/.drush/drush.ini (so located in the site user's home directory) to ensure the value matches the php-fpm php.ini e.g.
post_max_size=256M
upload_max_filesize=256M
These values should be picked up by drush when it is run via a cron job or in a user shell.