So she's really working on including it in her program... Best of luck to Liza!
3A-3T is somewhat more valuable due to the GOE factoring (compared to what it was in 2010). However, giving +1 or +3 is not based on difficulty, but on execution. That's the whole point of GOE. Yuna got +3s at 2013 Worlds even for relatively simple jumps, like 2A. Mao never got a pass on her GOE despite being the only woman to do 3A--in fact, I'd argue she kinda got hosed because they compared her 3A to the men's. Plenty of people not named Adelina get high GOE for 3T-3T (Liza, Yulia, and Alena come to mind... in fact, Yulia's SP scores started going downhill when she added back the 3Lz-3T due to edge/GOE/rotation problems)
The whole "judges would have some predilection for something new if done correctly" was a 6.0 thing. COP today is better about this than it was in 2010, but it's still not a system that makes a combination like 3A-3T worth the risk. You have to consider that even Midori wasn't a machine--3A-3T takes a lot of energy, and could have consequences for the rest of her skate. It's much smarter to do 3A-2T if she wanted a second 3A, and then doing a much easier 3S-3T. No BV loss, maybe a GOE loss but not much of one, and less energy required.
Frankly, all of this is unnecessary because Midori had excellent 3-3 combinations that would earn huge GOE. Under either 6.0 or COP, she wouldn't need 3A-3T to win. Trying it could actually cause her to mess up and drop down in the standings.