More square footage than what? Is this assuming that the space at low level, that would be occupied by the platforms, could not be used for anything else?
No the aim was to have small footprint station leaving more land clear for other development unfortunately unbeknownst to Rishi's hotel room team those potentially "clear" areas can't have very tall buildings, hence tall buildings are needed to maximise overall development floor space (which they they are when sightlines are included) then you have to have you have to have tall building over the new HS2 station further east if possible where the top of the building can be much taller.
The problem is that this is expensive and Camden council viewed all this extra cost for over station development as something that meant they should get more S.106 benefit from based on % value of overall non rail exclusive development where as everyone else view was that Camden should get less because of the restrictive planning conditions.
In reality Rishi didn't get any real vote bounce out of it and Euston tunnelling isn't meant to start till summer 2025 so not much cost impact now (cheaper than cancelling for short term cashflow which is mostly what they care about at the moment).
Euston tunnelling should start shortly after the eastbound TBMs from Northholt complete their work.