your understanding is wrong

Say you do leave on time, but do not hand in the I94, you will be recognized still in US, and probably over-stay after your I-94 date is passed.

So if you already over-stayed, no matter you hand in your I94, the CIS system has already labelled you as over stay. The only difference is how long you over stayed. If it is a couple of weeks, it might still be OK. but 180 days you will be banned to enter US for 3 yrs. Over 1 yr, ban for 10 yrs.