This error usually happens when you get banned or something happened. Anything you did before this error occured?
This mechanic has existed for a very long time. It is not so much due to you being "suspicious" but rather as a flood control mechanic. Even Diablo II would temporarily ban your IP if you overloaded their servers too much, changed characters too often or made too many new games in a short time.
Were you refreshing a lot? Or swapping between chat and game list a lot?
Yes refreshing too often will get you IP banned. It is flood control to try and prevent potential DoS attacks or wasting server resources.
There is no "auto refresh" when looking for a game. Once the game list is refreshed (button at top of screen) the server streams all games at a certain rate to you based on ordering inside a queue. This is how slot refreshing used to put your game up on the list as it would reinsert you in the queue. Manually refreshing forces all game results in the list to be retransmitted so likely triggers flood control prevention if pressed too much. It is possible that if you subscribe to the game list update stream too long it also triggers flood control prevention.
