Yes, the exchange reveals that Allenby is willing to overlook just about anything, abandon just about any principle and ethic in order to achieve an end. Lawrence gets things done in service to that end. Therefore, Allenby wants him back at the front no matter what he confesses in that room. If anything, I believe the earlier scolding about how dangerous it is to "act on your own initiative" rather than acting on orders from above is the more cast-off line in the scene. I believe it was put there in order to provide cover for what follows in the sense that the filmmakers did not want to portray Allenby and the entire British military command as utterly unprincipled regarding the means to an end while the more intense and focused exchange between him and Lawrence immediately afterward would support that conclusion.