Bastila is not a reliable source.
When two sources both state the same thing, regardless of reliability (and Vandar is reliable), with no signs of contradiction, then I don't see any issue on why it's not true.
Malak retreating instead of destroying Revan like every other opponent we see him face says otherwise. Revan was able to duel with Revan where as no one else was.
Star Wars Knights of the Old Republic Prima Guide implies Darth Malak did this to ensure "one-on-one combat" would occur.
If you payed attention to the dialogue before hand, he was rather pissed that many Sith doubted he could beat Revan.
The fact the guide says "returns through the blast door" rather then "retreat" further supports my claim.
Also, it is worth mentioning that the guide says Malak goes away from Revan once *Revan* gets some injury, not vise-versa like many say.
There is also the fact that all books, Bastila, Carth, and Malak all say Revan must "retreat" from Malak in order to survive.
The fact that Malak had to resort to stun to finish Revan off shows that even then he was a formidable opponent for him.
Not at all. If you played the game, you would notice Bastila Shan comes out immediately after Revan is in stasis.
Malak would have felt her breaking from his hold, and then stopped the fight with Revan in order to defend himself against Shan.
It is only logical for him to not fight the both of them when he can easily just beat them separate. Carth agrees with me.