re:Never said it was...
the point is Methane and Lox RL-10s work and just need a little more R&D and they went to a lower performing Hypergolic solution which lowered the throw. Then They choose RS-68s over SSME which they have dozens of ready to use. All because they wanted to avoid the expense of more R&D.
On another related subject It is reasonable to assume SSME can be started mid-air just as any engine. They just need testing which cost money.