I know we're talking about EASA in this instance, but if you check the CAA Examiner Lists you'll find all the DHC6 examiners are either FE or CRE. None are a TRE. Those Examiner qualifications require an underlying FI or a CRI.
https://www.caa.co.uk/commercial-ind...xaminer-lists/
The question was can a CRI teach for a DHC6 Type Rating, which they can. You'd only need a TRI (SPA) for a high performance, single pilot aircraft. Which if you check the document I linked above, would be something like a Honda Jet, Cirrus Vision Jet etc etc..