In the old and not so old days this was mostly true but now things have changed.
Winchester was the first to introduce an all-plastic hull, the Compression Formed Winchester AA. Remington followed later with the Unibody hull, the inner dimensions and internal case taper mimicked the AA so closely that data for one was data for the other. All though Remington has made several different one-piece hull since then, the Unibody is the only one in production today. This is the hull used in STS/Nitro Gold/Gun Club/Sport Load, Nitro Express and Sportsman Steel factory loads.
In 2004 Winchester introduced a new AA hull and called it the AA High Strength hull, abbreviated as AAHS. This new hull is a three-piece hull with a separate hull tube, cupped plastic basewad and brass (AA) or steel head. This construction follows the Reifenhauser pattern except the basewad is a taller cup shape intended to follow the same inner taper as the original AA. Winchester uses the same basic design with a steel head in the Universal,Super Sport, Super Target and Super Speed factory loads. According to Winchester then and now, you may use the older AACF data in the new hulls.
One of the first things you discover is that it is not always true. The AAHS hull is shorter and has less internal volume than the AACF and the many of the older loads simply do not fit in the new hull. Solutions include using a wad with higher capacity than the load calls for, such as a 1-1/8oz wad for 1oz shot, and using denser powders that take up less room in the hull.
The Remington Unibody/STS hull is basically the same as when introduced. All the old data for it, and nearly all for the AACF is mostly interchangeable. Careful study of the reloading data tables will show this clearly. Data developed just for the new AAHS hull (apparently very little is around, most data sources pre-date the 2004 introduction) would also be safe in the Remington Unibody.
Remington Unibody/STS or Winchester AACF data at the very top of the pressure range may not stay under SAAMI limits in the smaller capacity AAHS hull. These loads may not blow up your gun but depending on the components they will be a tight fit, or no fit at all, in the AAHS.