BTW, I meant westwards, not eastwards

Isn't the problem that Broad St was on a viaduct while Liverpool St is in
a cutting? The approaches are also in rather different directions.

....firstly, yes, which is why demolition was required.

....secondly, yes, but for a few hundred metres or so they are both
heading north until the eastern line turn east, easily enough for the
throat required for the new platforms.