Inconsistency between geonames website and API data

[jrocket]

Looking at at the city of Leeds, UK (Geonames id 2644688). Wikipedia reports the population as 516k. When I look at Geonames website I see population is also 516,298: http://www.geonames.org/2644688/leeds.html

However when I query the premium API getJson endpoint

http://api.geonames.org/getJSON?geonameId=2644688&style=full (username removed)

I get:

{

...

    "geonameId": 2644688,
    "toponymName": "Leeds",
    "population": 455123,

...

}

Why am I not getting the same figure as shown on the website?

Looking at other cities the population seems to be off too, Manchester, UK : Geonames (id: 2643123) says 395k population whereas Wikipeida says 550k population (as of 2021).

I've been a premium API subscriber for a numer of years and always assumed basic data like city populations in the UKs largest cities would be correct or at least relatively up to date so I'm a little dissapointed to find these errors and inconsistencies. How often is the data updated and is there any reason that I'm getting one statistic via the website and another via the API?

Thanks