Okay I think I get it. My thing with the 120% isn't just that Yuji, Todo, Mahito are 120% stronger, its that 120% state can't be scaled to others as this state is a new level for them, its something unlocked from BF which makes them completely different from their past self as that's basically said by the
narrator,
Todo and
Nanami that hitting BF makes you into this new person who gains better ce control and more knowledge. And given this is the first for Mahito and Todo it makes it all the more appropriate not to say their base is slightly below it. I think the use of potential makes this apparent, if it was like Nanami's OT making him
output 110% to 120% then I'd agree with scaling their base to it but it's not, its about potential meaning their 120% potential is much higher than a simple output increase.