confusion about skiplist test method

A newer to leveldb，I've read the db/skiplist_test.cc recently and has some confusion about ReadStep method for concurrent test.
WriteStep(..) seem to insert into skiplist among K insert point. ReadStep(..) read initial_state at begin，and iterate the skiplist to get the newer version in bucket k，in order to compare newer version with initial_state.
So, here occurs some confusion.
1. The method only take **sample read** to verify if there some version conflict，but indeed we want a method that check **all the insert point** to cover all unexpected result.
2. ReadStep func get the initial_state at the begin, but it does not get the lasted state in later read while loop. That is to say, the function only check the state some time before, instead of check the state immediately after write.

wish you response~
thanks