Not just Schwinn, but lots of others. It has caused great confusion over the years. If you go to THIS ST. SHELDON'S PAGE and scroll down to Tubular Tires ("Sew-ups"), you'll find an explanation for the confusion:

Tubular tires are mainly used for racing. A tubular tire has no beads; instead, the two edges of the carcass are sewn together (hence the term "sew-up") with the inner tube inside. Tubulars fit only on special rims, where they are held on by cement.

Tubulars existed in 6 different sizes, but only two of them are readily available these days.

- Full-sized tubulars fit rims of the same diameter as 622 mm (700c) clinchers. This size is sometimes referred to as "28 inch" or "700". It is also, confusingly, sometimes referred to as "27 inch." The "27 inch" designation is inaccurate and obsolete, but you'll sometimes run into it in older printed material.

- In clincher tires, there is a real difference between "700c" and "27 inch" sizes, but for tubulars this is a false distinction. Whenever you see mention of "27 inch tubulars" the writer is actually referring to standard full-sized tubulars, as used on most racing bikes.

- "26 inch" or "650" tubulars are smaller, mainly used on time-trial or motorpacing track bikes.

- "24 inch", "22 inch" "20 inch" and "18 inch" tubulars are sizes formerly used for children's racing bikes, but pretty much extinct these days.

Tubulars are also sometimes called "sew-ups" or "tubs" (British usage.)
If you want to sound like an ignorant yahoo, call them "tubies" or "tubeless tires."