BB,
I am saying that NUH theory is to wait and see if the D3 embryos can survive thru D5 or longer for freezing cos according to their experience most embryos after D3 kinda of dies off if there are not strong enough to grow further but since your embryos did not go pass D5, you dun no if there are strong or not, maybe they can grow further and different clinics do things differently, just take what we share here as additional infor for reference, take it with a pinch of salt, what we offer here is what we experience and what we hear, not the fact.
dun worry about D3, D5, remember as long as they get implant, they are good and what made them implant, most importantly I think is the condition of our body when we are doing the ET, so you shd concentrate on "tiao" your body, then whatever quality of embryos can get implant easily. Like my dr said at this stage, it is the implantation that matters since we already know that there are formed embryos but implantation is a question mark to even the specialist, it still boils down to our own womb condition, the soil for the seed lor.