Hmm hundreds of laptop batteries in a datacenter doesn't seem too smart.
What would be more pertinent is changing the charging logic so the packs are held at 50% state of charge vs being always charged up to 100%, that will significantly decrease the chance of pack issues while greatly increasing the longevity of the battery itself. If you hold a lithium ion cell at 50% SOC for years without varying it and keep the temperatures flat, it can last for a very long time without capacity degredation. If you leave it at 100% it will be degrade in a few short years and can swell, at which point it has twice the chemical potential to flame out. Also if it's charged to 100% when the datacenter is at 20'C ambient and datacenter cooling fails and temps go up, having the pack warm up to 40'C can overvolt it and that is usually where they swell/fail.
Also fair to note here that Apple is probably at the frontier in terms of using the highest safety cells and battery management logic so I'd feel better about this than I would putting a lesser brand's lipo pouches in datacenter environment.
A lot of words, many of which might well be true. But it ignores the fundamental point.
I think we can safely assume its not their building, not their datacentre.
As a result, they need to play by the rules of the datacentre operator.
The datacentre operator has fire suppression systems build to a certain spec.
The datacentre has risk assessments and insurance covers to think about.
The datacentre has other customers to think about.
The datacentre has its own staff to think about.
Yes, datacentres have some of the most advanced multi-layer fire detection and suppression systems in the world.
But a fire caused by multiple racks stuffed full of LiPo batteries will likely result in very hard to control results, especially if it becomes a cascading event.
Yes, it is arguably highly unlikely to ever happen, especially with Apple hardware as you say.
However at the very least the guy should fess up and have a chat to the datacentre operator to at least give them a chance to say (preferably in writing) "ok, no problem, we'll just add it to our risk register".
Its The Right Thing To Do (TM).