Only our bag with food was searched..both before we checked in, and after. No other bags had the notices in them. Now I know better. SW has asked that you not pack food in your take on luggage..they said it slows the process. And anything I can do to keep the process going and not take up the searchers time, is OK with me. Maybe it depends on what it is. Mine was hot chocolate and oatmeal. Here is what they have to say from their site (while they haven't banned it, they have asked you not to carry food on SW in checked bags..the checker mentioned he wished they would ban it, because they don't like going through the bags and touching people's stuff, anymore than we like it touched).
From SW site:
Customers are urged to leave their checked luggage unlocked, which will avoid the potential need for TSA personnel to forcibly open bags that require further physical inspection. Plastic zip ties or cable ties may be used if desired.
Customers are asked to:
Not pack food or beverages in checked bags
Pack footwear on top of other contents
Put personal belongings in clear plastic bags to reduce chances of a TSA screener having to handle them
Spread out - not stack - books
Leave gifts unwrapped should screening require them to be opened.
Put scissors, pocket knives, and other sharp items in checked luggage.
Put film in carryon bag because screening equipment will damage undeveloped film.
Avoid over packing your bag so that the screener will be able to easily reseal your bag if it is opened for inspection