This doesn't sound right to me. We had an XT/286 and I don't recall any expansion card involved. Wikipedia seems to agree with me that it was a totally separate model. That being said, it doesn't include a citation for the info, so it's possible it's incorrect.
The '286 expansion cards were not IBM products. they were produced by third parties to give the older XT performance approaching the AT '286 computers.
https://en.wikipedia.org/wiki/IBM_Personal_Computer_XT