No problem but why extend it EVEN FURTHER to mustard??
It was not extended “even further”. There is a common belief that the original takanah was to forbid specific named species, but there is no basis for this belief in any pre-20th century source. Every pre-20th century posek, as far as I know without exception, says that the takanah was against all species that fit the criteria, and one of those criteria is that all species that grow in pods are forbidden. Therefore, since mustard grows in pods, it is forbidden. End of story.