The post title may be a bit misleading here in the sense that the linked article isn't claiming that only the X-700 had aperture priority.

While I can't comment on specifics of the availability of aperture priority in 1980s SLRs, the two models you mention (t90 and n8008) are late 80s models (86 and 88 IIRC) where the X-700 was released in 1981.

The X-700s are terrific cameras, I shot with one for many years.