dura ace triple crank gearing question

Hi, I'm thinking about converting my road cranks

I mainly want a triple set up so that in the few hills I have (short and
sharp) I can spin rather than stand (my 35 year old knees!), but I also like
to put the hammer down on the flats when riding in a group and don't want to
be undergeared.

My question:

why does shimano offer ultegra in triple as 52/42/30t

but dura ace only in 53/39/30? campy record has a 52/42/30 combo as well
dont they?

does any one find that having a 39 middle ring with say a 12-23 seem to be
too easy to spin out on the flats?