Ok, I do start to understands your complaints about the GTFS, from my point of view it's a mistake that temporarily not used stops suddenly disapear.
Can you describre the systemic quirks of this file on OSM Wiki and explain to avoid such pitfall ? I will try to get the file improved.
(If you want) You can also add comments & requests for fixup on stops that can be retrieved with overpass turbo; not to clutter the wiki.

I will do a survey.

undreground metro station would tipically get a low (<100) ref:STIB_MIVB

I think I will review my 100 items lists, moslty to see if they already exist as De_lijn stops then it's mostly done.

stop like this don't need to be added:
7520,,"DEFACQZ",, 50.828554, 4.362114,,,0,

https://www.google.com/maps/@50.8284903,4.3622959,3a,75y,191.07h,88.53t/data=!3m6!1e1!3m4!1s8oslnzRCAw6WVgyvSHvE0g!2e0!7i16384!8i8192

We can agree we don't agree but I've seen exactly the same things at other places with "wxyz;wxyzF" as reference, even with only the tram passing through center lane. So it's hard by looking at patterns to see what is wrong or right.
Creating non-existing objects from GTFS would be the worst. I will do some survey soon :-)

I've been there many times as my colleague lives there and we did some "homeworking/coworking". The tram line 19 is split in two and a very short replacement bus runs on a part of the same route, also numbered 19. The stops that ends with an F (xxxxF) are mostly the one for tramways while the same number without F is for bus. In this precise case the bus stop is not permenantly marked, more likely a stop mast on a concrete block, which would be temporary anyway. The reference without F can be used anytime the tramway is out of service. For me it's okay if they map to the same platform; it's the next best thing than having some loose reference.
I actually get to go around outside a lot in my work (*) and don't trust random data. I have even found some mistakes like a bus stop inside the water at "Etangs d'Ixelles" I will ask about.

(*): this is what we do at the moment: https://www.lalibre.be/regions/bruxelles/2022/05/04/des-annonces-sonores-aux-arrets-de-bus-et-de-tram-a-bruxelles-le-nouveau-dispositif-de-la-stib-pour-les-malvoyants-2BAAC44HE5DFVOMUHZNGZM3V2Y/

please explain why it's wrong and what would be the right way
osm.wiki/Key:ref:STIB_MIVB

ok. What is the difference between a bus and tram stop ?

"SAINT JOSSE"
this seems completely right but 1582 does not exist in the OpenData GTFS.

On the other way,
2889 do exist but at "Rue Willems" which seems wrong
2889,,"SAINT-JOSSE",, 50.849717, 4.375378,,,0,

I'm confused :-)

stop 1287 does not exists

Hi,
"POMMIER" is 1484/1487

I found there was a duplicate using Overpass Turbo + this query:
----
cat patch.osm | xmlstarlet sel -t -m "/osm/*/tag[@k='ref:STIB_MIVB']" -n -c "string(@v)" | tr ';' '\n' | sort | uniq -d

Hi, I'm not really "dumping" any info, merely just adding the "ref" (or should it be "ref:IBXL" ?). I'm planning to automaticaly reconcialte the two datasources (I'm build a huge ETL anyway), so changes will be tracked.

I just wanted a minimal set of data in before going further. This editing is about the places around my office so I know this neighborhood very well.

I would be pleased to go to some meetup but there's no emergy, I will put it on hold until this happens.

Greetings