Keywording and rating a few photos triggers XMP update of all pictures in the catalog

Hello all

Software Lightroom Classic 12.2.1

Mac OS Monterey 12.6

I have  the option "Automatically write changes into XMP selected". My catalog has more than 100.000 photos. I see that, changing keywords or rating a few of the picture will trigger the update of ALL catalog's  pictures XMP instead of doing it for the specific photographies that have been updated. With the catalog size, this is a process that consumes plenty of time. 

Any advice?

Thank you very much for your support

Albert