In my experience some wild callery are completely compatible and others are incompatible completely. This thread gives an example Wild callery pear rootstocks. The tame callery seem to be exact clones and compatible from williamette nursery. I like wild callery for many reasons but as an example i had a very wet area so i dug up callery from a similar area with @39thparallel we tested them and they worked 100% there in my wer area and in his.they can also tolerate drought. I enjoy t-budding as well as traditional grafting it seemed very easy but @fruitnut is a great teacher T-budding tutorial - #108 by JesseS . As an example no branch bending was done but this callery quickly produced fruit. The scion wood grew identical to the callery branches i cut off. Interesting influence the rootstock has over the tree.
I have used many interstems through the years looking for the right one such as improved kieffer, small yellow unknown pear, douglas , clara frijs etc… here is a a little of what i grow for pears Here comes the 2019 pear harvest!