That's...yeah, like you said, strange. Why two different holders though? It isn't like TK has a full-time branch outside of Japan, or does it? Some kind of holdover limbo from the previous owner, maybe?
I'm interested in this now. I need to look this up.
TMU, Tommy Kiara sought to build the ZZ in the UK, & there was a partnership later on with the Rowen brand to build aftermarket parts that ended in dispute. According to Wiki, the brand's ownership, Genuine Tommykiara Studio, partnered with JDM Parts Ninja to start selling parts again; GTS sells the parts in Japan & JDM is the exclusive distributor overseas.
Additionallly, Wiki also states the owner base dwindled in Japan, so GTS & JDM PN helped the local clubs form into an international club b/c many cars were being bought & shipped out of the country, so I presume there's a large, but perhaps quiet, following outside Japan.
This is also from Google's AI, but it makes sense: with the brand focused solely on tuning than their own cars these days, GTS/JDM may have zero interest in licensing the old cars. The ZZII design was also sold to Autobacs when they bought the company, which could further complicate licensing (interesting enough, Autobacs has also been absent from Gran Turismo since 6).
Edit* I do think having Japan as setting would be the perfect time for TK & the other tuning brands FM2 featured to return, but I feel it's such a long shot. Many are in TXR, but I think that's due to Genki being a Japanese studio with easier connections to those brands.