Extend docs

docs/999-big-list-of-options.md

@@ -1712,7 +1712,7 @@ Allows to manually define a list of function names that should always be conside
 
 This can not only help with dead code removal, but can also improve JavaScript chunk generation especially when using [`experimentalMinChunkSize`](guide/en/#experimentalminchunksize).
 
-Besides any functions matching that name, any properties on a pure function and any functions returned from a pure functions will also be considered pure.
+Besides any functions matching that name, any properties on a pure function and any functions returned from a pure functions will also be considered pure functions, and accessing any properties is not checked for side effects.
 
 ```js
 // rollup.config.js