Hi Ethan, I believe there are two schools of thought about this.
One is that a Flat response will let you hear the recording as is. The other, with the Bass tip up and HF roll off, is intended to better represent the 'average' domestic listening situation which will have booms, possible soft furnishings, lots of warming (and confusing) reflections off hard surfaces and so on.
I had a chat with someone at PMC some time ago about this. I had a pair of their monitors on approval. Their plan is to deliver a 'flat' response very evenly throughout the listening space. Part of this plan involved a HF boost on-axis, then keeping the tweeters high and not toed inwards, so that the listener was never on-axis.
Their speaker, the IB1s was the best I have ever heard, with just the one problem, too bright. They suggested using a Sony speaker controller as many of their clients do. They added that it was commonplace to use different Eq's when mixing for different output. For CD one might use our curve, for TV a stronger HF roll would encourage brighter mixing. For film, the X curve. Strangely they didn't tell me I could BIAMP them with only a second amp, no crossover etc. needed. I would have kept them!
I borrowed this little pic from our friends over at studiotips, I am hoping they won't mind. There is a page there called Understanding RTA, which promotes this type of tailored response. Remarkably like the old B and K one, I thought.
Best Regards, DD