I have got BFP with both 3dt and 5dt unfortunately they all ended in m/c.
My FS would rather grow the embryos to day 5, but if they are starting to fragment a lot, they encourage you to freeze at day 3. By doing this they hope the natural environment of the uterus and not an artificial one will allow these embryos to grow.
Tigger! Can K'iesha do some of her magic and get my AF to appear????