schools with BArch and MArch

What does it mean if a school like Cornell has both? Does it mean you can only declare as a BArch or is there a BS Arch option if you want to do a 4+2 MArch program?

Cornell doesn’t offer a BS in architecture or architectural studies. Students graduating with a BS or BA from Cornell or any other college may be admitted to Cornell’s MArch, no matter what their major.

Cornell’s basic MArch curriculum covers 3.5 years;. Admitted students with BS/BAS or BArchs in architecture are allowed to apply for “course equivalency credit” which will shorten the time involved in getting an MArch.

This is what Cornell says:

Other MArch schools have what is often called an MArch I, 3.0 to 3.5 years for students without undergraduate degrees in architecture and an MArch II, 2.0 to 2.5 years for students with BArch or BS/BAs in architecture. The names of the degrees and requirements VARY WIDELY, so if it seems confusing that’s because it surely is.

that now makes sense why I hear posters mentioning 6-8 years to finish their MArch