Great catch! Renaming the tag to [tag:jvm-groovy] as you suggested is a good idea. Editing the usage guidance should also be done if the tag is renamed, but just fixing the usage guidance alone is very unlikely to prevent the tag from being misused. 

Version tags are available (although some folks feel they should not be used at all) in the form [tag:16.04] [tag:18.04] [tag:20.04] [tag:20.10] etc. Usually we have synonymised them so that, for example, [tag:xenial] maps to [tag:16.04] (attempts to use the former add the latter). We could do the same with [tag:groovy] if we rename the current [tag:groovy].