Did Tauroneo know the Black Knight?

[Areth]

It is quite obvious that Tauroneo knew Gawain, and when Ike told him that the Black Knight killed Greil, he showed some surprise that the Black Knight had become so strong.

The implication seems to be that Tauroneo knew the Black Knight back when he wasn't so strong: maybe back when he was Gawain's student, before he became the Black Knight.

Or am I misinterpreting things?

[Fëanen]

My interpretation is more that he was familiar with the Black Knight, but still considered him far below Greil's abilities (especially since he didn't know that Greil had disabled his sword arm). In other words, he knew that the Black Knight was good, but never would have guessed that he was THAT good.