I've read a post elsewhere today that repeats the claim that, in 1932, Indian batsman C. K. Nayudu hit a six that went over the River Rea at Edgbaston and therefore travelled from Warwickshire into Worcestershire:
"His most famous knock came against Warwickshire, where he smashed 162. One of his sixes famously cleared the River Rea, the natural boundary between Warwickshire and Worcestershire. So literally, he hit a six that travelled from one county to another!"
Although the actual hit seems well documented, I am not at all sure that the River Rea was ever the boundary between the two counties.
I recall that in 1964, well before he played for Warwickshire, the great Rohan Kanhai hit a six over the river. He was playing in an end of season game for a West Indies XI against an England XI. I'm not aware of anyone else achieving the feat.

Back in the day, there were many enclaves and enclaves of counties but it seems very unlikely that the former Colts Ground was ever in Worcestershire.
The Rea does rise in Worcs so it's possible that it forms the county boundary somewhere upstream, which could give rise to this confusion.