I got the email stating I could order. So, I ordered a CT around May 27th. Got an email stating July - Sept is when I could expect it. Then, I got a message wanting to schedule delivery for June 4th :)
So, yes, it _can_ come earlier, but not sure if anything specific triggers it.
What I've noticed is that it will charge the charge limit, then if the temperature around the CT increases, your charge level will increase. I've seen this on both the CT and Model 3 LR AWD. You _may_ see it go the other way when the temperature drops significantly.