Your example is very relevant as it's both very real and also extremely specific to your own world and context.
Trying to predict every potential 'trigger' imposes a major mental burden both on the authors/editors to find them and on the reader in the distracting way it's prominently appended to information
If you're talking to a very specific audience I don't see anything wrong with it. But making it a common/general practice seems like a completely wasteful exercise. Especially with the way the grievance crowd is never satisfied with only a few people getting special treatment, the list always grows exponentially. Then eventually there will be a mountain of trigger warnings for every potential niche.
So if we agree there's some very real (growing) costs involved, the other factor is does it provide real benefit for x% of readers? Then you can evaluate the ROI. If studies show people are even more likely to read it anyway (or maybe can't "prepare" themselves in a meaningful way) it's hard to see much benefits vs costs.