MacOS mdfind/mdutil issue and updatedb command : how to index all the files on the /Volume (root /)

A simple question : on Linux, updatedb command which is launched a second time seems not to reindex all the hard disk.

On MacOS Catalina (or maybe for previous), it seems that the command sudo /usr/libexec/locate.updatedb reindexes all.

Is there an option for locate.updatedb to only update what's new ?

I thought about doing : sudo /usr/libexec/locate.updatedb -u but I am not sure.

mdfind is a great tool but has got no transparency about its dameons mds : I said this since suddenly on my MacOS, mdfind stopped finding recent files, and it was very frustrating. Moreover, it takes a long time to index all the Volume (several days in my case, 2TB HD).

So I wonder if locate.updatedb command that updates from what is already existing is possible ?

On Linux systems, where updatedb is performed, this command is very quick because the whole database is no reindexed.

I just want not to reindex all the /Volume at each time I launch locate.updatedb on MaOS.

UPDATE 1:

I have killed all mds and processes relaled to mdutil and mdfind. Then, I launched yesteray a :

mdutil -E / :

here what I get when I do a ps aux | grep mds :

$ psu | grep mds
root 9607 0.0 0.9 11835260 285804 ?? Ss 9:20PM 2:14.29 /System/Library/Frameworks/CoreServices.framework/Frameworks/Metadata.framework/Versions/A/Support/mds_stores
root 9606 0.0 0.2 6866808 71984 ?? Ss 9:20PM 5:27.05 /System/Library/Frameworks/CoreServices.framework/Frameworks/Metadata.framework/Support/mds .

I don't understand why it doesn't return all files which normally should be found : example with mdfind -name README, it only return a partial of the expected result (nothing is displayed into my $HOME).

Moreover, the loop glass on right top indicates that indexing is fully carried out but from my opinion, this is too fast, I have 1.2TB of data of index : is it normal, what do you think about this ?

Any suggestion/explanation is welcome.