As many say the comment that was deleted, I will say this.
In this hobby, people tend to combine into one group all "stars" including true seastars (Class Asteroidea) and brittlestars (Class Ophiuroidea). These are two TOTALLY different groups in terms of their needs and requirements.
Brittlestars in general can be spot fed and can go in much smaller tanks than reef safe seastars such as Linckia. This is truly and apple to oranges comparison. There is no similarity.
In the wild, you can find sometimes hundreds of brittlestars in a small area. They commonly can be found living under the same rocks in the reef. It is not an issue to keep multiple specimens because they can coexist and can be spot fed.
The limitation with Linckia is purely due to the feeding issues of needing large surface areas of LR. Apples and oranges. Nothing similar.
I certainly do not say you can not keep echinoderms in less than 100g because that would be idiotic. Echinoderms include seastars, brittlestars, sea urchins, sea cucumbers and sea lilies. The latter are a poor choice for tanks, again due to dietary needs. The basketstars, a type of brittlestar, are also typically unsuitable due to diet and more specifically large size.
But cucumbers, urchins, brittlestars and certain seastars - echinoderms all - are absolutely suitable for a mature tank, even of small size. The limitation on Linckia, Fromia, and Echinaster is entirely due to its dietary needs.
Of course the micro brittlestars in our live rock, along with the seastar hitch hiker Asterina, are so common that I likely have several hundred or more echinoderms, even in my 45g tank.
If you feel the need to "call me out" at least be accurate in your details of what I say and when.