Spawn protection not working as it should

I noticed spawn protection is not working the way it used to.

Here is the scenario.

I created a new multiplayer server, I did not change any of the settings.

2 players joined the world. We are both able to break/place blocks (This should obviously not happen, we should both not be able to place/break blocks)

I op'd player A (myself)

Player B is no longer able to place/break blocks within the spawn radius. (note: Player B tried to place a block of sand, this is cancelled. I (player A) can still see the sand block in player B's hand, but Player B appears to have nothing in their inventory)

Player A is obviously able to place/break blocks since they are op'd

When I de-op player A, both player A and B are able to place/break blocks.