I'm going to continue this, as it's so striking. Sorry it's gonna be long and complicated.
This post refers to Apple pictures (on the Mac), no longer to Notes, but the issue with search is very similar to the one experienced in Notes. A moderator may want to edit the title to Notes & Pictures.
Anticipated conclusion: search in Pictures is broken (as in Notes). Or designed badly.
New picture in the library. Its title field is 'Schiff in Venedig' (German for ship in Venice. I'll continue with the German terms in case someone wants to reproduce exactly).
No tags, keywords, location, people contained nor added. The AI algorithm did NOT identify a 'Schiff' in 3 days (but that's OK and not the point of this post - but important to understand there was no index for 'Schiff' created for this particular picture).
I performed the following searches:
'Schiff' ==> not found (but 158 other pictures containing a 'Schiff' were found - identified by AI, so I assume contained in the index of the library)
'Venedig' ==> found (I don't have 'Venedig' in any other picture in my library. No tag, no title, nothing)
'Schiff ' (trailing blank) ==> not found, but 'Schiff in Venedig' proposed for search
'Schiff in' ==> found, and proposed
Then I continued and created a tag 'Schiff' and assigned it to the picture from Venedig. After indexing complete:
'Schiff' ==> 159 pictures (now including the one from Venedig) found instantly
Tag 'Schiff' deleted.
'Schiff' ==> 158 pictures only
So why does it find 'Venedig' and not 'Schiff' - as both are in the title field only???
Theory: if it doesn't find a search word in the index (containing tags & AI identified), it continues to search in the title fields. As I have many 'Schiff's in the Index, but no 'Venedig', it stops after finding 158 'Schiff's - but goes straight to the title field, after not finding 'Venedig' in the Index.
To further investigate, I created a tag 'Venedig' and assigned it to a different picture (NOT to the one with 'Ship'.
The search for:
'Venedig' ==> the newly tagged picture found instantly - but no longer the one with 'Schiff' (but it was found before the tag 'Venedig was created - see above)
'Vened' ==> both pictures found !!! So the STANDALONE term 'Vened' was not in the index, therefore continued to search in the title field (but as it was found as a substring of an indexed word, why not also show it (maybe that's how it works))
'Venedig ' (trailing blank) ==> found the newly tagged only, but displays the Venedig/Schiff picture in search proposal.
I think that proves the following:
when search word found in index - stops, no further search
when search word not in index - continues search in other fields
when search word found as substring in index - displays picture & continues search in other fields
But: apparently, in all thinkable search situations, it may show a proper search proposal - which is good, however, there can be MANY proposals, and the small window does not show EVERYTHING. And, results are shown only for words BEGINNIG with the search string (eg 'Vened' - yes, 'enedi' - no),so it's easy to overlook things.
So maybe this 'works as designed'? However, I consider that a severe bug, as having to keep all these 'rules' in mind and always obeying all of them, alternatively not being sure to find all elements one is looking for, is totally unacceptable imho.
This is highly complex, and I'm still not sure that I have looked into all possible variants and made the right conclusions. But shouldn't this be a very basic and totally easy to use and to understand feature of every app/database that has a purpose in life, to quickly and reliably find all elements that a user looks for?
I tried to send Apple feedback on my findings via the feedback site, but am not sure I was able to explain the case properly, due to its complexity. And no, I do not want to go through the regular support structures again, as this is a complete PITA once you already reached the level of insight into a problem like I did (I think), and until you get to a person who is smart an wants to understand the issue.
So honestly, I don't know what to do about that, other than writing about it here.