This is not anything new. Bill's theory is pretty straight forward and has nothing to do with the actual weight of the ubiquitous "lighter tandems".
Originally Posted by Ritterview
In part it pertains to the steering geometry found on most of the lightweight racing tandems, e.g., Calfee, Paketa, and Co-Motion in particular (nominal 73* head angle / 44mm fork rake), and the influence of additive rider fatigue associated with keeping said tandems with longer steering trail in a straight line over the course a ride. To a lesser extent, it also pertains to the veritical compliance, or lack there of that some of the racing tandems exhibit.
With regard to steering, the point he typicall makes is, while many riders like the cornering & handling "feel" that said racing tandems provide, 98% of most riding happens in a straight line or gentle curves where longer steering trail provides no signficant benefit. However, longer steering trail can be the source of additional "work" for captains since any side-to-side movements by the tandem team will require countersteering inputs by the captain to keep the tandem going in a straight line.
A Santana (nominal 73* head angle / 55mm fork rake)-- as well as any other tandem that uses shorter steering trail such as a Cannondale (nominal 73* head angle / 53mm fork rake) and to a somewhat lesser extent Co-Motion's tandems with steel forks (nominal 73* head angle / 50mm fork rake) -- will typically require less focus and steering input to keep the tandem going in a straight line.
Note: If someone would like to see just how much influence short vs. long steering trail has on how a tandem's handlebars react to lean-induced steering inputs, push a longer-trail tandem around a parking lot with your hand on one of the saddles and note that you can pretty mush make it go exactly where you want just by moving the saddle left or right of center. Now try to do the same thing with a Santana. You'll find the Santana will not respond in kind to those same inputs via the saddle and, instead, must to be walked and steered with a hand on the stem / handlebars.
Over the course of a metric, full, or double century rides it is therefore argued by Bill -- and probably correctly so -- that a given tandem team and the captain in particular could be less fatigued and riding stronger towards the end of a long ride on a tandem that is perhaps a couple pounds heavier but with shorter steering trail vs. an uberlight racing tandem with carbon fork featuring 44mm of rake. Couple that with what may also be a less compliant frame and a given team could have a higher average speed / shorter time on course if they rode a tandem that put less physical demands on the riders.
Again, it's not the weight of the tandem per se, it's the steering geometry and to a lesser extent the compliance of the frames that are at heart of the comparision and contrast that Bill has been making since well back in the 90's.
Now, as to whether or not this has any merit to a given team, that's highly debatable. Anything related to a rider's preference for things like handling / frame compliance is far too subjective and open for debate lacking any really good data that might quantify the differences. How a tandem is used also factors into the discussion.
Disclaimer: We've ridden long steering trail tandems since 1998 and enjoy the way they perform. I've also ridden quite a few Santana tandems and they also ride quite nicely. It takes a few miles to acclimate to the subtle differences in handling. What the Santana gives up in very aggressive cornering performance it compensates for on steep climbs. Everything in between is preference driven.