I've heard references to a 1991 GXL in a few different places. I was under the impression that in 1991 the GXL and GTU models were merged into the Coupe. Is this an error on my part?

 

If you read this topic:
https://www.rx7club.com/new-member-rx-7-technical-256/specifications-what-did-2nd-generation-rx-7-come-w-options-standard-features-963417/
You'll have the answer to your question.

 

Well it seems that in 91 there were three. The Coupe, Convertible, and TurboII. So why so many references about 91 GXL's? I didn't see anyone else saying anything so I though I was missing something. Thanks for the link.

 

Mazda may well have made the GXL in 1990, but if the dealer was only able to sell some of those in 1991, then they will be registered as 1991 GXL, although they were built in 1990 (at the factory).
That happens with almost every makes, not only Mazdas.