Well, it is kind of lame to mark my own answer as an answer....
Regardless of that, thanks to the amazing Twinmotion community at facebook I managed to find out 3 things.
1) Many users of Twinmotion 2019 with Archicad 22 and 23 are reporting DirectLink issues. Some even pointed to only use the feature to wow clients in special occasions (when they dared!).
2) The only truly reliable workflow is .fbx export. This was vouched by Tianxiao Wang from TM's Community Manager department. She even assisted with finding out how to remove DirectLinked geometry from ArchiCAD. You have to MERGE to a new file so that geometry becomes editable/removable, etc.
3) If you use the replace geometry feature to an imported .fbx file (your project's outdated version, per instance) you can then relink to a new .fbx file, updating the project. This prevents you from losing texture editing work which was applied to the previous version of the project.
Hope this helps someone. Thanks to all those who tried to help, both in this community as in Twinmotion's. Cheers all!