I am writing this reply mostly for people that might land here by search.
If you delete your game, you will lose all visibility the game has gained. Deleting removes all comments. It makes a hole in any collection the game was in and people do not know why, if they even notice. It also removes all ratings.
Using the same url does not change this.
And if you have purchases on the game, it gets a lot worse. Your customers can no longer access the game. That is unprofessional and basically a tos violation. Itch and you would be liable for refunds
The game also loses all trust it has built. It can lead to people reporting the game. It might look like a hacked account, an impostor or like spam. It might also result in quarantine for the suspicous behaviour. It is suspiciuos. There is no good reason to delete a game to update it. But a lot of bad reasons. Like getting the benefits of having a new game. I have seen developers get restricted for this type of gaming the system.
If one makes significant changes, there is devlogs for that. They can even bump a game to most recent again sometimes.
Your topic's title complains about something being done without notice. Everytime you did remake your game page you messed up all the collections of your 4k followers without notice. There is a collection counter on projects.