I think what this is. Let's play house and pretend I am a forum moderator today. Now see me give a profussional answer...
It is
the Reconstruction Mode. It "remembers" your last reconstruction "version" even if you build something new after that last version.
If you click the "crane" to enter reconstruction mode, and then decide you don't really want to reconstruct anything, and so you exit with absolutely no change, then it is OK. But if you pick up even one tile of road and put it into the "side bar", your reconstruction "work in progress" will be remembered -- for ever -- even if you have built something new, such as a cherry garden, after that (forgotten) reconstruction.
So, at the moment, you have to click "Revert All Changes" (the third button below) to discard your previous, long outdated reconstruction "work in progress" (which was registered before you built the cherry garden).
In a sense, the "revert" button is also a "update" button how the current reconstruction mode works