If you ignore the wheelchair symbol the Dalston Junction symbol looks the
same as the Mile End or Finsbury Park symbols , both of which are cross
platform interchanges.

I note that Hammersmith has also been changed so that the District and
Hammersmith & City stations are joined as one station. I am sure that at
one time they were not. Does this show some change in policy on the part of
LRT . Is it to indicate that Oyster recognises that travel via those
stations is an interchange?

The number of circles at the interchanges appear to have no meaning For
example Baker Street, which is all one station, has two now, wheras West
Hamsptead, which is a Jubilee Line station and an entirely separate North
London line station (originally West End Lane) only shows one.