It IS just a marketing term...
Right here in the bay area lotsa folks are digging up old 700c touring road, cross, and hybrid frames - and putting on so called "29er" tires without issue. The same is being done with CF frames that have steel or ALU forks. A popular rim choice appears to be the Sun MTX33 - built onto Phil Wood MTB single speed hubsets.
My favorites are the folks buying Raleigh framesets with White main paint and Red logos/lettering. When finished up with Red or White saddles, tape, pedals, grips, etc., I often think: "Old School Budweiser". I even told one guy this and his response was literally, "Exactly!"
They know what they are working with, they know what their 700c tube and tire choices are - and they know "29er" is just another "cool" trendy marketing term.
=8-)
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5000+ wheels built since 1984...
Disclaimer:
1. I do not claim to be an expert in bicycle mechanics despite my experience.
2. I like anyone will comment in other areas.
3. I do not own the preexisting concepts of DISH and ERD.
4. I will provide information as I always have to others that I believe will help them protect themselves from unscrupulous mechanics.
5. My all time favorite book is:
Kahane, Howard. Logic and Contemporary Rhetoric: The Use of Reason in Everyday Life