Surely there are no signs left at Waterloo which dates before the
dreadful c.1990 re-signing project which wiped out 90% of the
Underground's signage heritage?

More likely this is a case of the new corporate ID rules taken to the
extreme. In the past the gaps between station 'ticks' was either
compressed or extended to allow the vertical line to fill most of the
enamel diagram.

After around 1990 the distances were more standardised, and if this
meant 75% of the sign was left blank, so be it!

Mind you at least one hanging glass sign in a Bakerloo Line lower
escalator circulating area had a painted out 'Camberwell' destination
below 'Elepant & Castle' and I have the photo to prove it.