Personally, I thought the buffering system was too forgiving, everytime I was trying to input a 236B I would get a 623B because of a previous move I inputted.
Also, as for the question about usng 623B as a good oki tool, I've personally been using it as a way to cover myself so I can charge Kinako's spirit meter. Anyone rushes you down while that thing is floating around is going to eat a big damage combo, It knocks the person down and enables you to OTG them with anything if they get hit. So if they stay away until it goes away, you can charge 2 of your gauge back for the cost of the move, plus one more.