Reb, I believe any kind of starch can attract bugs. This is because starch is made from organic materials such as potatoes, rice, corn, etc. Sizing is chemically manufactured and therefore does not attract bugs, but sizing stiffens fabric considerably less than starch does.
A lot depends on where you live. In warm, humid climates where there are a lot of bugs then storage of starched fabric might present a problem. In MN and WI it has been a non-issue for me. Some of my starched fabric has been stored for years without attracting bugs.