If you place a LCB anywhere, it will automatically stop spawning in that block range. My default LCB settings are set to 51, and on the block itself you can pick to actually show the box area I mentioned. Inside of a high rise you get the same expected results, but you still have this massive space of sleepers that can still spawn above that line at the top.
To summarize, while the block is active you're pretty safe.
During a16 and a17, I paid attention and noted that hordes spawn primarily on the ground. What I suppose what happens is that anything above you will still spawn after its normal refresh time. However, during horde nights what I suspect happens is that there is a cap on mobs that can be in any given chunk, and any active blood moon mobs are subtracted from the sleepers above your block claim range.
I have not tested a high rise in a18.
I apologize for my late reply; life can be a wasp sometimes, and the years have whittled down my attention span, to something that would probably pale in comparison, to that of a decorated Goldfish. No offence to Goldfish people out there.
...besides, I'm a South American tropicals guy myself. And no, I do not feed my fish Goldfish...
Moving on...
Thank you so much for your very interesting post. I think you may be right about the Blood moon nights. In previous Alpha releases, there were problems with horde capacity on Blood moon nights. They were... tepid. I agree that the devs resolved this by basically doing what you said. Suppressing spawns, to create flow for directed spawns.
I've tried several test games now in A18, across all experimental releases thus far and haven't seen a re-spawn within the claim block shield. I also have a bed roll down at all times and it is never 5 blocks from the claim block.
Even though we know this is a game, even though we know we are tethered to the reality we drift from while playing it, on a psychological level, there is nothing that will drive a player further from it, in my opinion, than the very mechanics, cheated them out of their sense of accomplishment. An accomplishment that was achieved within the logical rule set, as presented to the player within the game.
I'm actually enjoying the game. I think who ever took hold of the wheel, after the ♥♥♥♥fest that was Alpha 17, (my opinion) understood that the best way forward was to head into the storm. I don't think it is a perfect release. However, for the first time in years, I see the fingerprints of wisdom.
Peace to you yours.