I would not say that I have "made it up", rather that my suggestions are repeating accepted advice on small scale coal storage for domestic purposes.

Or put simply, modest stocks of coal should be well ventilated so as to keep it cool. This does indeed entail loss by slow oxidation.
A pile of a few tons should never self heat by more than a couple of degrees, this not only limits the slow loss of the fuel by oxidation, but also effectively eliminates risk of spontaneous combustion.
My source for this is a coal research council leaflet published decades ago in the UK.

(For large coal piles such as found at coal burning power plants and containing thousands of tons of coal the approach is very different. Such large piles cant be effectively ventilated so as to keep the temperature down.
Instead air is excluded so far as possible in the hope that the slow oxidation will soon consume the oxygen in the pile, without raising the internal temperature too much. The small amount of air entering should hopefully produce such slow oxidation as not be dangerous.
Means of limiting air ingress include packing or compacting the coal tightly, building piles with gently sloping sides, sealing the pile with a slurry of ash and water, and building wind breaks around the pile.
These techniques are not that reliable and fires in large coal piles are a known hazard.)

I give the above info contained in brackets ( ) in the interests of accuracy and completeness, but it is not relevant to domestic coal storage.