Yes, you have understood correctly. The choke and output transformers are about 60% heavier and give about 2/3 of an octave deeper bass, both frequency response and power bandwidth. The magnetic core laminations are M6 grain-oriented silicon steel, probably better than the original.
Subjectively it may or may not be very noticeable, depending on the rest of your system and choice of music.
For what it's worth, the new iron was developed because the original mass-produced line output transformer was discontinued, as was its replacement a year or two later. We decided to use custom parts, and I took advantage of the opportunity to improve the design.
