I want to say 90% of the people who ask me about applying Round 3 want to do it because they can’t stand the idea of staying another year/minute at their job. And the applications I often read for Round 3 looked like they were slapped together after your boss said you had to work the weekend.
Many Round 3 candidates gave little thought to their post-MBA goals (though it seemed clear they didn’t want to return to their current employer!), their terrible GMAT was either taken for the first time the week of the deadline or will be submitted the day after the deadline. The letters of recommendation read like text messages. He’s really g8!
Now, a lot of people think, well there is nothing wrong with applying in a rush in Round 3 and if I don’t get in I will apply Round 1 the following fall. But here is the thing, the admissions office will read that terrible R3 application before they read your shiny new R1 application. So your introduction is the worst version of you. Also, you might be inconveniencing/annoying your recommenders by asking them for last minute recs. Re-applicants do get in all the time, but they usually present their best selves each time
I know you want to quit your job, but unless you are in the top 10% at work AND were summa cum laude in college, wait till Round 1 and quit the day after you are admitted.