did the test in a clear wp installation
OS: Darwin 19.6.0 Darwin Kernel Version 19.6.0: Tue Aug 24 20:28:00 PDT 2021; root:xnu-6153.141.40~1/RELEASE_X86_64 x86_64
Shell: /bin/zsh
PHP binary: /usr/local/opt/[email protected]/bin/php
PHP version: 7.4.23
php.ini used: /usr/local/etc/php/7.4/php.ini
MySQL binary: /usr/local/bin/mysql
MySQL version: mysql Ver 15.1 Distrib 10.6.4-MariaDB, for osx10.15 (x86_64) using readline 5.1
SQL modes: STRICT_TRANS_TABLES,ERROR_FOR_DIVISION_BY_ZERO,NO_AUTO_CREATE_USER,NO_ENGINE_SUBSTITUTION
WP-CLI root dir: phar://wp-cli.phar/vendor/wp-cli/wp-cli
WP-CLI vendor dir: phar://wp-cli.phar/vendor
WP_CLI phar path: /Users/waltercruz/devel/clearwp
WP-CLI packages dir: /Users/waltercruz/.wp-cli/packages/
WP-CLI global config:
WP-CLI project config:
WP-CLI version: 2.5.0
~/devel/clearwp ? /usr/local/opt/[email protected]/bin/php -m|grep gd
gd
~/devel/clearwp ? /usr/local/opt/[email protected]/bin/php -m|grep imagick
imagick
Same result: webp is only generated through web interface, not by cli.