Heard of it but never seen one. Shimano does have a history of trying out lots of new things, which are theoretical improvements but some do not prove popular and are quietly dropped, like the 10mm pitch drive train. On the other hand, I have a very early Shimano indexed rear derailleur which uses 2 cables to actuate gear changes, which has been somewhat refined since then!
Heard of it but never seen one. Shimano does have a history of trying out lots of new things, which are theoretical improvements but some do not prove popular and are quietly dropped, like the 10mm pitch drive train. On the other hand, I have a very early Shimano indexed rear derailleur which uses 2 cables to actuate gear changes, which has been somewhat refined since then!