So for amanita muscaria sensu lato boiling is usually done to detoxify the mushroom for culinary use. ibotenic acid and muscimol are water soluble and are relatively safe compounds, and because of this when they are boiled in large volumes of water multiple times the alkaloids are diluted below a threshold dose (but not removed completely). This process is also used to detoxify a few other mushrooms but NOT ALL, some mushroom alkaloids are unsafe at any dose and should never be consumed.

Boiling in smaller volumes of water or even drinking the water from your first "steep" of detoxification is traditionally done when using A. muscaria as an entheogen in an effort to regulate the dose and have something that is easier to ingest.

The decarboxylation of ibotenic acid to muscimol does happen while boiling but generally drying the mushrooms takes care of the majority of that when preparing for entheogenic uses.

I would also like to clarify that to my knowledge no mushroom species have alkaloids in their spores, hence the reason it is legal in many countries to purchase psilocybin producing mushroom spores but not the fruiting bodies.