In the meantime I was busy firing up an unmodified trilogy client to have a look myself... oh well!
https://youtu.be/LnQtajrxtGQ
For reference, the gequip.s3d from the Trilogy installer dated 2001-08-15 has zero in the "sphere radius" field, just like Titanium's. So the client definitely changed how it interprets the particle data at some point.