More or less, yes. CLI, offline, no need for a cloud account. Used ast-grep successfully to locate bad code blocks (dynamic typing, don't even get me started) and also to replace them with others. Highly recommended.
At work, we use it for enforcing a bunch of custom lint rules configured as a yaml file committed directly to our repo, entirely cloud-free.
(I may be overreading your comment as suggesting that these were reasons to use ast-grep over semgrep.)
I have used `ast-grep` to devise my own linters with crushing success.