Question, does
Dome A (Argus) at 81° S, 77° E = 80 S and Longitude 90 East,
81° S, 77° E = approximately 80° S, 90° E, so, to answer your question, yes. How accurate was that 80°S, 90°E reference? I bet you don't know. Do you know if they even located the high point of Dome A, or only knew they were in the general area of it (on the scale of a continent)? I'll bet the answer to that question is no.
Are they at the same spot???
Apparently. Dome A is what was reported. Here's what was said:
Four United States planes flew from New Zealand to McMurdo Sound on Dec 20, 1955, and made exploratory flights over unknown parts of the continent until Jan 18, 1956, when they returned to New Zealand. These flights proved the inland areas to be featureless in character, with a dome 13,000 feet high at about latitude 80°S, longitude 90°E.
"About". If you think they meant latitude 80.00°S, longitude 90.00°E, you're simply mistaken.
They reported results from a project to explore a large, featureless, previously unknown area that found a high point culminating at 13,000 feet, somewhere around 80°S, 90°E, based on a month's worth of long-distance recon flights over a vast plateau, with each flight requiring a return to base. The reported location is almost 1,000 miles from McMurdo (great circle distance), the actual high point is even further, and they had a vast area to explore; how dense a pattern do you think they flew? How rounded off is that mention in passing in a general-purpose encyclopedia? Why not do some research and see if you can find how much data they collected over that 1955-56 season and where they flew?
Sure sounds like Dome A (13,428 ft) to me.
If yes, then you should go work for NASA
The United States Antarctic Program is funded and coordinated by the National Science Foundation, not NASA. I'd love to go back to Antarctica on a project, but I was 40 years younger four decades ago and I doubt they want to be responsible for someone my age now, even though I'm still in good health.
Any more questions?
I take it you haven't located the '70s version of that encyclopedia, so you still haven't confirmed if the 13,000+ foot dome is "missing".