How to set compilation flags/qualifiers?

I have the following problem:

• There are several classes with method generators, which needs to be compiled during every compilation
• I have "ckub" qualifiers enabled in studio
• I don't want to remove "u" qualifier because I need it very much in another namespaces

So how do I force classes with method generators to recompile when "u" qualifier is present?

Currently I solved this problem by setting studio qualifiers setting to "cukb /checkuptodate=expandedonly" which solved my problem, but I'd like some clarification as to why it helped. Here's  checkuptodate qualifier description:

Name: /checkuptodate
Description: Skip classes or expanded classes that are up-to-date.
Type: enum
Enum List: none,all,expandedonly,0,1
Default Value: expandedonly
Present Value: all
Negated Value: none

Questions:

1. What is an "expanded class"?
2. Why explicitly setting /checkuptodate=expandedonly forces classes with generators to compile every time?
3. Is there any other, cleaner way to force classes with generators to compile every time?