It's not possible to clear (or purge) the variation/alias of images. ( probably since LiipImagine Bundle )
There was this Issue: https://jira.ez.no/browse/EZP-23518
Then, after the fix the warnings are gone but the Alias/Variations are not deleted, the feature itselt was not tested...
1/ the clearing doesn't work because it was based on the legacy expiry
2/ the purge doesn't work because of the source code.
I've already talked about this issue with Bertrand D. he confirmed there is work to do on this subject
I will create a PR with a workaround to open the discussion. ( I know you won't keep this workaround )
And last subject, the liip imagine cache remove command doesn't work either with eZ, probably because image paths are different for each contents ( I didn't dig this last behavior)
I'll put the link to the PR in comment.