It appears that [r=0] variable isn't viable in the latest snapshot. Commands with the selectors @e[r=0] and @a[r=0] simply will not work. Furthermore, there are no in-game "command was unsuccessful" messages when a command with said selector is run.
Linked issues
duplicates 1
Comments 1
See https://bugs.mojang.com/browse/MC-95352?focusedCommentId=285905&page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#comment-285905