First, I don't think sega's trademark was voided, it is more like "It is not a violation of a companies trademark to use it when they require using it to access

First, I don't think sega's trademark was voided, it is more like "It is not a violation of a companies trademark to use it when they require using it to access the device." That is, the registered trademark still protects everything else it is intended to protect. Second, that was the US ruling, I have no idea of how the rest of the world, specifically japan, views using a trademark like this. I do know japan is weirdly(at least to US sensibility) strict about copyright and trademark law. So it was an attempt by Nintendo(and Sega) to have a legal crowbar to use to control third party use of their system. In the US it was ruled that this would not work for Sega. So Nintendo probably never used it for that purpose (in the US)