The one that laid 364 eggs in 365 days would not have been typical even then. There would have been plenty of other Australorps that laid fewer eggs than she did.From my understanding about the Australorps the one that laid 364 eggs in a year was from the old genetics. Australorps almost were extinct & when they were being bred again to build the numbers up that was lost. Modern day Australorps only lay around 250 eggs a year now I think...it's been awhile since I've looked up Australorps tho.
As for how well Australorps lay at the present time, that depends on what numbers you are looking at. For example, I can find these numbers on various hatchery pages:
250 eggs/year https://www.hoovershatchery.com/BlackAustralorp.html
260/year https://www.idealpoultry.com/product/1493/2
200-280 eggs per year https://www.cacklehatchery.com/product/black-australorp/
5 eggs/week https://www.mypetchicken.com/products/baby-chicks-black-australorp
"best" egg production https://www.mcmurrayhatchery.com/black_australorps.html
From My Pet Chicken, 5 eggs per week would make 260 eggs per year if it happened every week of the year. I am guessing they took average yearly production and divided by the number of weeks in the year, but I could be completely wrong about that. They could mean 5 eggs per week during good weeks and no eggs at all during molting and winter.
From McMurray, "best" is their highest category of egg production, and includes things like Sexlinks and Leghorns. The text description of Black Australorps also gives high praise to their laying ability.
It is quite possible that Black Australorps from one hatchery may lay better than ones from a different hatchery.
It is equally possible that each hatchery tested laying ability under different conditions, which can give different results even if the hens have the same inherited laying abilities.
And it could be that each hatchery got their numbers from someone, and posted them on the website without actually checking their own flock for that ability. I know that hatcheries often list standard weights for the various breeds, when their own breeding stock and the chicks they sell do not match those weights, so they might do something similar for the egg production numbers.
I don't know about old vs. new genetics for Australorps. You certainly could be right, but I just do not know either way.