Why this CG over a BThrow-DThrow CG?
In order to properly answer this question, let's first deconstruct the components to each CG:
In the Bthrow > Dthrow CG, you have the following elements:
1. Popo Back Throw > Nana Regrab : The issue with this element of the CG is two fold. First, the bthrow has variable timing. This variable timing from character to character is compounded by difficulty because the inputs to throw with Popo and grab with Nana are too close together to reliably visual cue. At the same time, the issues with the sync mechanics creates directional issues when attempting to soft turn. This is reflected when you see Nana spinning in weird directions if you attempt to soft turn the CG in a non-buffered manner. If done out of a standard hard turn CG, Nana could trip. If done at an improper timing, Nana could possibly dash grab.
2. Nana Dthrow > Popo Regrab: There are two issues in this part of the CG. First, because of the cool down buffer mechanics, you could successfully regrab while accidentally buffering a Nana grab out of the cooldown of Dthrow. This is circumvented by shield buffering, but shield buffering then leaves you open to things such as accidentally inputting a spot dodge or roll because Nana acts on a cue timeline that isn't in real time. At the same time, you have to input down before walking forward to adjust spacing for the regrab. In some cases, most notably in the light characters, this causes a problem in spacing because the character will go through crouch and then proceed to walk forward.
Now let's deconstruct this newer CG combination:
1. Popo Fthrow > Nana Regrab: There is a constant timing for each character, so it can be done reliably on visual cue AND muscle memory. The only draw back is that spacing/timing is tighter than the B>D CG
2. Nana Bthrow > Popo buffered turnaround regrab: This creates a situation where the variable timing of the CG can be done purely on visual cue instead of trying to feel out the CG as per a Popo Bthrow. It is also a tripless turnaround. This also does not require shield buffering.
Both are good CGs. One however is tripless and can be done almost entirely off visual cue while the other cannot say the same.