That sounds about right, I remember talking to my Dad about it at the time and being surprised that they were still available even then. He remembered the situation at EMI in the very early fifties when the board decided that LPs were a temporary fad and they would just carry on producing 78s. A year later they had a largely new board and a crash programme to produce LPs, He had a number of the earliest EMI LP test pressings from around 1951, now mine.
This
https://www.amazon.co.uk/dp/B00E6KE4P2/?tag=pinkfishmedia-21 cover picture shows an acoustic recording horn, balance achieved by carefully positioning players closer or further away from the horn.