Such "Twin Lateral" reinforcements were fairly common on taller and heavier-duty French touring bikes of the mid-to-late 20th century, and have been featured in Bicycle Quarterly. They're generally found on bikes intended for carrying heavy camping loads (hence "Campeur") rather than, say, a "Randonneur" intended for more moderate loads and more "spirited" riding. It's not unheard of to see lighter-duty bikes with reinforcements, however, especially if they're intended for bigger/stronger bikes. I even recall seeing a racing frameset from an Italian builder of a very large size that featured Bombadil-esque reinforcements.
Here's another example of a French Campeur:
Hard to say if such bikes were an inspiration for Breezer #1, maybe somebody can ask Joe Breeze next time they're at the Marin Museum. It wouldn't be impossible, given cycling's popularity in the Bay Area, that he might have encountered such a bike before building his own.
Grant designed a custom with true twin lateral reinforcements back in 2014, except they were "tentacular" in that one curved up to the seatstay and the other curved down to the chainstay:
It was for a relatively short rider who wouldn't normally have warranted such reinforcement on their frame but I recall it was a specific request from the customer, who was enamored with the "tentacular" diagatube setup on the Proto-Appaloosa/"Mystery Bikes" (which were the genesis of the whole "long chainstay" ethos, but that's another thread). She was a former list member who went by the handle "Riv Chica Warrior," IIRC, and she had won the frame in some kind of raffle that they held back then. Grant didn't feel there was enough room on the headtube to braze in a full diagatube so he went with the smaller diameter twin laterals.
-Jeremy Till
Sacramento, CA
On Monday, March 6, 2023 at 6:38:03 PM UTC-8 J J wrote: