The actual timing of the rehab work will (to maximize your return) happen BEFORE you use delayed financing for your cash out refinance, but AFTER you have closed on the property as an all-cash buyer. YOU HAVE TO FUND THE REHAB WITH YOUR OWN CASH FIRST within the 6 months, even after paying for the property all cash to begin with, if you want it returned. So if you buy a house day 1 in cash, plan to rehab it, but go day 2 to get a 70% LTV refinance for example, you can do it but you can't get paid for rehab money that you think you might be spending. Now, IF you SPEND that money, you can still get 70% of it back in this example, say if you did rehab and it took 2 months and you went to refinance 2 months and 1 day later. I think that is the direct answer to your timeline question, is it not?
Think about this: you and a buddy get creative in robbing a bank. You buy a burned down, "could be" million dollar house for 100k and say it needs an estimated rehab of 900k, you close in cash for a hundred and go to the bank for 700k (70% LTV). The bank grants the loan and you run off to some other country with 600k profit and leave the property for dead.
I believe you may be thinking its a little bit like a 203k loan in some sense but I don't think delayed financing allows for any draws and so the rehab timeline is at your choosing within the 6 months, but you only get paid if you ALREADY put your OWN cash up, and it appraised right.
Not an expert but, pretty sure that's a good understanding. So its really your choosing to go sooner and get less, or do your rehab and go later but get more. Hope that helps.