why stone watchtower does not mark the field with culture/ownership like wooden watchtowers do?
see screenshot
1 = wooden watchtower, 2 = stone watchtower, 3 = wooden watchtower, 4 = wooden palisandes, 5 = stone watchtower (while the stone watchtowers get buid automatically 25 turns after built wooden watchtower. Means, while wooden watchtower are borders not able to pass for other, now, after 25 turns, the fields are passable with stone watchtower. Need to destroy all stone watchtowers and build wooden new, all 25 turns)
Edit: 2 turns later, next wooden watchtowers are stone woodtowers, but now one stone watchtower (the 6) kept the culture/ownership of the field. (1 = wooden wt, 2 = stone wt, 3 = storne wt, 4 = stone wt, 5 = wooden palisande, 6 = stone wt
Don't see any logical reason for such, so I suspect it's a bug
Edit 3:
2 turns later, destroyed stone tower No 2 and built wooden watchtower again, but field gets not back the ownership and culture. So my suspect that it is a bug, looks to be confirmed.