I noticed that every updated installer has no galaxy installer (anymore(?)), this is why I asked.

Interesting thought so I tested the updates of the games I own. Unfortunately your theory does not seem to be correct. Grim Fandango Remastered i.e. is one of those games that have received a new installer and it still has a Galaxy Installer that can be chosen.

Edit: My mistake - Grim Fandango was not even updated. Further testing confirmed your thoughts. Not a single one of the games I own that has been received an installer updated recently also has an optional Galaxy installer.

Timestamp of Grim Fandango Remastered installer was Dec 13 2017 (1.4.0_(17097)).
I just extracted it with innoextract.
I think it does not use the obfuscated filenames like recent updates.

Oh dang - my mistake. Grim Fandango was in the list of the updated games but it was not updated - only the website was. Will see if I find any game that really has been updated and see if Lin545's theory might still be true.

Edit:; Seems to be. At least I could not find a single game I own that has received an internal installer update and still has offers optional Galaxy installer as well. So what could this mean?

https://www.youtube.com/watch?v=ca-e5MrVbVU

That people like me that prefer to unpack the installers are basically screwed.

I've noticed it myself - the first two installers seem to be corrupted - the second file is only ~490MB in size if I remember correctly. Parts 3 & 4 are in fact the correct installers. Guess it's something for Judas to fix/get fixed :).

I was not asking what the consequences are with those updated installers because it has already been posted here. So even if you are right, it was not my question.

I was following Lin545's observation and basically confirmed that the Galaxy installers are in fact gone for those that has been updated recently. So the updates might have a positive effect but I am not quite sure tf the conclusion that GOG wants to go away from Galaxy installers is the right one. I also don't know how a different packing algorythm could make Gaalxy installers obsolete.

Some GOG game updates have no official update flag.
I started to record it since Nov 2017. Only games I have are listed here. [1]

Report for Mar 2018:
Total updates: 135
Games updates: 123 (Some games have multiple updates, daily basis)
Flags I got: 126

93% updates have an official flag. 7% are missing.

[1] Mar 2018 record: https://pastebin.com/S37sekeF
[2] Feb 2018 record: https://www.gog.com/forum/general/the_what_did_just_update_thread/post19169

Death Road to Canada windows version still has not received the FEMUR update from last week, all other versions got updated.

Simon the Sorcerer and Simon the Sorcerer 2 just got flagged. No new changelogs yet.

Linux and Mac installers are added.
This new installer is broken. GOG Support Ticket 235975.
Ref: https://www.gog.com/forum/general/adamhms_linux_wine_wrappers_news_faq_discussion/post168

It's broken in wine. I can't test it on real windows-pc, but in Virtual Box it's possible to launch game (with DxWrapper). On the other hand, 'Arcanum.exe' size definitely changed, so message in changelog: "updated internal installer structure, no changes to game file", isn't correct. Maybe in old installer exe was patched with unofficial patch? At least with patch applied game works as before (and exe size almost the same).

Kingdom Come: Deliverance

Updated to 1.4.1.
No changelog.

Ash of Gods: Redemption

Marked as updated.
No changelog.