Thanks for your feedback. You do raise a valid point, it does seem that you should be able to add a version value that is text-only. This version-equal-to filter will work with a version such as "1.0.0-pre", but not with text characters alone. It may be a case of either changing the logic here to allow text-only versions, or improving the help message so that it is more clear.
Do you expect to have more versions that are text-only? As a workaround for this case, you could change the version you send to be something like "0.0.1-test", then permanently ignore any crash reports with the "test" tag.
Let me know if that could work for you.