Clarify _set/_get description

[KoBeWi]

Closes #70205

Note that a property must be present in [method get_property_list], otherwise this method will not be called.

So this note is wrong, but not entirely.

See, _set()/_get() are called when calling set()/get() on an object, with property name that doesn't match any built-in property. So you can do object.get("this_property_totally_exists_trust_me"), and _get() will be called with this property name.

When _get_property_list() matters is when inspecting or serializing the object. The editor/serializer must know that property "exists" and will call set()/get() on whatever is returned by get_property_list(). But if a property is not defined, nothing is stopping you from manually accessing it.

Feel free to suggest how to better convey this information. Or maybe the description is already fine, idk.

[Mickeon]

When _get_property_list() matters is when inspecting or serializing the object. The editor/serializer must know that property "exists" and will call set()/get() on whatever is returned by get_property_list(). But if a property is not defined, nothing is stopping you from manually accessing it.

That's crazy because I genuinely could've sworn to have been insisting about this with you and Yuri back in the day before the description was changed with how it is now.

[Repiteo]

Thanks!