Expectations don't conform in the legal documents either sometimes, even if they exist. Thankfully it didn't cause any issues, but my last house deeds clearly showed that I exclusively owned a small wall on the party boundary.. and the neighbour's house deeds also clearly showed that he exclusively owned it, too.
A while back I spent a lot of time looking at houses for auction, and their deeds etc. Some of the older ones really showed the scope for things to be lost, overlooked and cocked-up over their history - being drawn up by hand as local solicitors saw fit at the time and kept, lost and updated by numerous random parties over the years. Ownership of the property itself wasn't always conclusive, let alone minor things like boundary walls and fences.