Originally posted by The Ellimist
He refers to "physical and emotional" challenges. It's not necessarily that he can't face him with a blade.Also, Vader could probably crush him in telekinesis.
Physical challenge would obviously include a Saber fight.
If he's holding back in telekinesis, then he's clearly not going all out on Luke, which is bound to reflect in the Saber fight as well.
Originally posted by Geistalt
In that case, Luke's sheer Force strength is even more impressive, since he was ill-equipped and only half-trained and still bested his father (decisively).
"he's not really equipped to do it"