The tag is present in Lintian version 2.104.244. That is the most recent version we know about.
Tag to attempt to measure the number of packages that might have an issue with arch:all binNMUs.
At this time, please do not attempt to "fix" the problem. It is not clear what the solution is (if any at all), nor is it clear that this is something that will or should be supported.
This tag is experimental.
This is a classification. There is no issue with your package.