This is very likely true. Even incandescent bulbs and lanterns put out some blue, but when properly dimmed, they aren’t putting out much, and the total light levels are low.
The behavior seems to be sort of an integration curve of “spectrum, intensity, and time.” The default with LEDs in a house is “Lots of blue, bright lights, all evening long” - unless you’re staring at a screen, in which the whole inverse square thing works against you too.
Having less blue is good, but “less blue and still very bright” will still screw with your cycles. Having less blue, and far dimmer lights, works a lot better - and a quick glance at a phone message coming in, or flicking (in our case) the pantry lights on for a few seconds doesn’t seem to cause problems. I don’t have too much trouble with a movie in the evening either, though as can be seen, our TV is small, distant, and (at night) dim.
But, yes, comparing with natural outdoor light cycles, even with a campfire, is a good contrast for “What our body does on natural light cycles” vs “What it does in our artificial environments.”
So go buy a bunch, if you have space to store them. I see two possible outcomes there: Either you’ve simply bought a lifetime supply of bulbs for evening spaces, or, once they’re banned, prices will rise significantly and you can sell them at the higher prices and, if high end LEDs with minimal blue remain a thing, buy some of those. There are places that claim to sell such things, they’re just quite expensive compared to the cheap hardware store LEDs.
You’ll be happy to know I’ve got some reviews of a few of those coming up. Stupid though it felt to join a lightbulb to my wireless networks, I’m doing it for science.
Short answer is “It varies wildly,” and “They do non-intuitive things.” On one of the bulbs, as soon as you go into RGB mode, it’s really in “dumb RGB mode.” You give it a hex value, it sets those values in the emitters, and does that. The color rendering on a RGB-sourced white is worse than a smoother spectrum white emitter, but they do what they claim on the tin.
Another type, though, will make use of the white emitter at the start, and will fill in colors with the RGB emitters to shift the average around. However, as you head out towards the red/orange end of things (or any direction, really), at some point it falls out of the center range, and shifts from “White emitter plus other LEDs” to “Pure RGB mode.” When this happens, even though your eyes don’t notice the change, you’ve gone from a fairly low blue peak to “Lots and lots of blue” - as you get more saturated in the reds and oranges.
As in pure red LEDs? Sure, they exist, the smart bulbs in “red only” mode work fine for it too, you just feel like having to walk around the house silently, making “One ping only!” comments in Sean Connery’s accent. They’re not quite mono-wavelength, but neither are they very far from it. It’s a far inferior experience, IMO, to just a dimmed incandescent running at 30% or something, which is very low blue, but also a smooth spectrum.
I have a whole series of posts on my kerosene lanterns and heaters!
The Blizzard spectrum mentioned in the post (slightly redshifted from the incandescent bulb spectrum) is one of my lanterns - it’s a proper incandescent source, dim, redshifted, and absolutely adequate to read by. I can read an e-ink reader with it with the frontlight turned off, though paper books do reflect a lot better. I read most of Greer’s Weird of Hali series by lantern this fall and winter, and it’s wonderful ambiance for it.
Safety… yes, they’re an open flame, but as I talk about in that set of posts, kerosene is quite safe as far as “burnable liquids” go. The flash point is high enough that even outdoors in the summer, 85F or so, you can wave a lit lighter back and forth over a pool of it without the vapors igniting. Hit the surface with the lighter, it’ll warm up enough to start burning, but the vapors at any reasonable temperature simply aren’t flammable. A spill is just a mess to wipe up.
I run a low sulfur kerosene alternative in the lanterns (to reduce some of the various side products produced), and I generally don’t notice them running in terms of indoor air quality on my particulate meters. Except the Comet. It’s cute, but for various reasons it tends to stink more while running - more than the rest of the lanterns combined.
So, I consider them safe, though they might be against some leases. I wouldn’t use a propane lantern indoors, nor some of the pressurized gasoline sorts, but a cold blast kerosene lantern, on a modern enough fuel, is quite well behaved.