I think he is saying "killing the horde would leave us a repair bill that we are not prepared to pay". I completely understand where he is coming from. I've seen what Demolishers can do even to solid Steel fortress bases. I am probably more prepared than Orclover is to foot that repair bill, but I fully understand his complaint. I've had horde nights with tons of Demolishers and I have tried to fight them "legit" (i.e no exploits). It isn't pretty once your gamestage is high, and especially in multi-player.
You are absolutely right that this approach presumes that killing the horde is the objective on blood moon. I would argue that it is absolutely is. ALWAYS. Why? Because avoiding the the horde - and just "surviving" - as you put it, is is no challenge whatsoever. To the point of being a no-brainer. Just pick one of the following:
a) Sit on top of a big POI, make it tricky for them to path up to you, and do not interact with horde till morning.
b) Get on your push bike and just cycle for 4 hours in a big circular road, and do not interact with the horde till morning.
c) Build a base that exploits the A17 AI with an infinite ramp or maze. Do not interact with the horde till morning.
See the connection between these options? Yup....do not interact with the horde till morning. If you are at a high gamestage and your horde will be 1000 zombies, and your Max Alive is set to 32, then you will have 32 zombies arrive. If you kill none of them, then no others can spawn. You will likely never see a Demolisher. Come morning just mop up the 32 who can no longer threaten you as they cannot run any more. Job done.
So why is this a bad thing? Because it is totally dull and challenge free? You might as well turn off the horde and save yourself the inconvenience of avoiding them. imo of course. If you disagree I would ask you simply this. Why bother with that minor inconvenience? You didn't face the challenge, you avoided it, which was extremely easy. Why bother? I genuinely don't get it.
Is he facing Demolishers yet? Here's the deal....until those b******s appear, just about any old base design can easily handle the blood moon hordes with little to no effort and no exploits. There's a rite of passage here (for those not willing to exploit/avoid and who want to legit FIGHT the horde). It begins when the Demolishers first appear and usually ends shortly thereafter in dejection when your beautiful fortress is in utter ruins.