Pine tar, along with lanolin, beeswax, and jojoba, are "fat wannabe" ingredients. They're soluble in fat for one thing. Makers may use them in significant amounts in a batch of soap, so it's important to account for the volume and weight they add to a soap batch.
In addition, these ingredients also react with alkali (NaOH or KOH). Some components in these ingredients may actually saponify a little bit to produce unusual types of soap, but the essential point is they consume enough alkali that you want to include them when calculating the amount of lye required for a recipe.
For these reasons -- fat soluble, significant volume and weight, and consumption of alkali -- they are treated in the calculations as if they're the same as regular fats. That's why they're included in the list of fats in soap recipe c@lculators and the amount of alkali they consume is handled the same as if it is a "saponification value".
Rosin is another "fat wannabe", but it is unusual in that it has a "saponification value" that's quite a bit higher than the other "fat wannabe" ingredients. It is handled the same way as pine tar, lanolin, beeswax, and jojoba when calculating a soap recipe.