Fixed docs for maybe_placeholders

docs/classes.md

@@ -34,7 +34,7 @@ The Lark class accepts a grammar string or file object, and keyword options:
 
 * **propagate_positions** - Propagate line/column count to tree nodes, at the cost of performance (default=`False`)
 
-* **maybe_placeholders** - The `[]` operator returns `None` when not matched. Setting this to `False` makes it behave like the `?` operator, and return no value at all, which may be a little faster (default=`True`)
+* **maybe_placeholders** - When True, the `[]` operator returns `None` when not matched. When `False`,  `[]` behaves like the `?` operator, and return no value at all, which may be a little faster (default=`False`)
 
 * **lexer_callbacks** - A dictionary of callbacks of type f(Token) -> Token, used to interface with the lexer Token generation. Only works with the standard and contextual lexers. See [Recipes](recipes.md) for more information.
 

docs/tree_construction.md

@@ -9,7 +9,9 @@ Using `item+` or `item*` will result in a list of items, equivalent to writing `
 
 Using `item?` will return the item if it matched, or nothing.
 
-Using `[item]` will return the item if it matched, or the value `None`, if it didn't. It's possible to force `[]` to behave like `()?`, by using the `maybe_placeholders=False` option when initializing Lark.
+If `maybe_placeholders=False` (the default), then `[]` behaves like `()?`.
+
+If `maybe_placeholders=True`, then using `[item]` will return the item if it matched, or the value `None`, if it didn't.
 
 ### Terminals